You have three choices when it comes to tuning the L67 engine:

1) Replace the PCM with an aftermarket version tuned to your specifications.
2) Re-write the PCM's code yourself.
3) "Trick" the PCM by using an AFC (Air/Fuel Calibrator).

There are companies (INTENSE, ZZP, DHP) that sell PCMs with generic performance tunes at farily low cost. Most if not all of these will not work for the Riviera, which has its own code. For $200 or so, the same companies can custom burn a PCM that will work, but unless you know exactly what you need, this option probably isn't the best.

Using a programmer such as DHP's PowrTuner software ($390) to write your own PCM code is probably the best option. With the PowrTuner you can actually tweak everything from the fuel curves, to the transmission's shift habits, to the speed and RPM limiters. It's the ultimate mod for someone who really loves their Riv. Check the Scans, Tuning, & PCMs section for more info.

The AFC, more specifically the Tech Edge Mini AFC 2.2, is a small box that gets wired between your MAF (mass air flow) sensor and the PCM. Sometimes referred to as a MAF translator, the AFC lets you to "fool" your PCM into adding or subtracting fuel from the air/fuel mix by altering the MAF signal in a controlled manner.

What the AFC does is allow you to in effect reprogram the PCM's MAFF (mass air flow frequency) table to get the fueling curve your engine needs to run with less KR. Usually this means adding fuel to keep up with all of the extra incoming air. The expected result is that knock will be eliminated and KR will go down, giving you back lost horsepower and enabling your engine to run more safely.

The AFC has been used with varying degrees of success. For minor adjustments to the fueling curve, it makes sense, but for larger fuel demands, reprogramming the PCM is the best way to go. For info on how to tune with the AFC, check the Scans, Tuning, & PCMs section.

what would it take to completly replace our PCM and wires from ,say a GTP? i see rivman had that done on his 95' (the one with the swap'd engine) and i was wondering what something like that may cost and if its easier/cheaper that a DHP PT? what all would need to be replaced?

Not sure that it would be difficult, but buying a separate PCM isn't cheap. I think they're at least as much as the PowrTuner, maybe less at a salvage yard. I do know that with a PowrTuner you can effectively change all of the transmission settings to that of a GTP. From what I know that's the biggest percievable difference between the cars.

I believe you would have trouble with the security system. It wouldn't be worth the trouble.

i would probably need a tuner or tech 2 just to make it work. thanks for the info, im just trying to research all the options and ideas.

get a powrtuner. its the best mod i've ever bought.

fyi, you can find used ones on clubgp.com. with the new software updates, the powrtuner is open to all 98-02 3800's, so if its set up for a gtp, it doesnt matter, as long as your riv is a 98 or 99.

is see yours is a 96. if you get a used one, make sure you're getting a good deal, because it costs $100 to add another vehicle (at least it used to, i'd check dhp)

oh, yeah, also fyi: i got a gtp pcm from a friend and swapped it into my riviera just for the hell of it before dhp opened up the powrtuner, and it did the typical thing where it would start but die immediately. i even flashed it to a regal gs, since that was the second vehicle on my powrtuner, and that didnt work. the regals use class II data for the gauges, so a wiring harness from them wouldnt work.

I'm seeing either a DHP or HPt (preferably HPt) in the near future (probably 2 months). I need it bad.

I just wanted to ask a couple questions to the tuner users that I don't necessarily feel comfortable asking strangers in the pro forums. I see that you can buy a bin from the vendors with their tune and they email to you (instead of buying the physical PCM). It costs the same amount as the PCM and with the same regulations as far as customization so that seems a little exorbitant to me. Anyway, I am curious to know what stops one from sending a tuned bin to someone else and then just editing the VIN with your programmer to use it in your car?

Secondly, As long as you have a laptop, you can have it with you and scan and graph everything you want right?

Thanks river's

You can definately find tunes and bins all over the place. This gives you the option of copying parts or the whole tune. For example the good spark tables from an 05 GTP are known to be the way to go then setup your tweaking around them.

With the HPT MPVI pro, (not sure on standard) you can scan and record w/o the laptop. All you need is the cable and little box. I think the DHP always needed the laptop.

Any reports on improved mileage for a 3800SC? I have been rolling this idea around for a while... downloaded software etc... But never really got excited enough to buy the interface cable and dig in. I like the performance I get stock, so my #1 goal would be to try to squeeze MPG's out of it.... without having to drive 60 in the interstate ... But 30+ mpg at 70-75Mph could get me VERY excited!

First: Buy software - it comes with cables needed to hook up to OBD2 port.
Second: Load software into laptop or mini-laptop for use as tuning tool.
Third: Learn how to use software. Manufacturer has excellent resources on-line and a community of experienced tuners to help.
Fourth: Start tuning your fuel and transmission shift points for better MPG at highway speeds.

I haven't done any of the above yet but plan on it in the future. I like how AA has been able tweak his PCM over the past couple of years to obtain good performance yet can cruise on the highway and get excellent mileage. Be prepared for an extensive learning curve.

Someone more experienced will chime in with more / other info I'm sure.