accessory tensioner hopefully

when i come to a stop light i noticed a grinding noise and i can feel the vibration from it and if i drop the car into neutral it goes away, when i rev the engine in neutral no noise or vibration only when my foot is on the brake and waiting for the light to change. I have replaced the small tensioner and the double pulley in the center it started to chirp a little. over the last 2 yrs i have replace cradle mounts motor and tranny mount... the pully on s/c has small bit if play in it... is there any way to check the accessory tensioner? Thanks for reading

As far as providing tension goes, there's a gauge built into the tensioner that shows if it is good or not. Here's what it looks like when everything is new -

awesome thanks for the help jack the R

The noise /vibration end up being a bad boost actuator, the stainless-steel rod was stuck in a upward position. replaced it and all is well