than '90-'92 with working AIVs. The point of AIVs was to reduce emissions because of the extra fuel the ECU added to smooth out the idle. The idle issues were resolved by '93 and they removed the AIVs and leaned out the idle program. '93+ cars did pay with a slightly bumpy idle. If you've driven a 90-92 car their idle is typically smoother, but the difference is slight.