which plastic part? the side or back? synthetic or carnuba wax?
dish washing soap can strip wax b/c of the grease fighters in dish liquid.(thats why you never use dish soap to wash your car)
clay bar can pull the wax up from the plastic, but be careful using it on porous or rough surfaces.
paint thinner takes off wax but be very careful!
"back to black" (made specificly for trim care) or a vinyl treatment (like armor-all) will cover it and make it look like it is gone. test it first b/c some oil/silicon based dressings can discolor the plastic. (like eagle1 tire shine)
time always works too
_________________
1996 with 254k miles, L32 4" FWI -> ported N* -> Ported Gen V w/3.0" Pulley, Stage 3 Phenolic I/C, ZZP FMHE, 1.84 RR, Headers and 3" pipe to mufflers, F-body brakes, and lowered on Eibachs. -RIP
AMG C400 White on black. Stage 2 w/E30 - 11.9@117 -daily