It's worth checking. I found it by spraying wd40 around the gasket area. Was actually a fluke, because I was checking to see if the brake booster line was leaking, but inadvertently sprayed wd40 onto the gasket and it made the engine rpm rise so I thought it was the brake booster line. Played with that and was very disappointed that it didn't make a difference. So tried replicating what I did before with the wd40 and eventually found that it was around the number 5/6 cylinder gasket was letting air in. Took the majority of a day to replace but I also replaced the collector gasket while it was all apart and it made a world of difference to the performance. The 4.2 efi engine is very smooth and quiet. Starts within the first half second of turning the key. Idles very smoothly.

