I know this is a Bonneville forum, but being there are some similarities between 3800 and 3100, and you guys have always been helpful and I'm kinda screwed at the moment (I've had the car for 3 days so far), I'm asking for any suggestions.

I replaced the lower intake gasket on a 3100. I've done a ton of these, so I do know what I'm doing. After putting everything back together, I have a backfire through the exhaust on cylinder #2. Keep in mind, on the 3100 you have to take the pushrods off to get the lower intake gasket off. I've swapped pushrods, rocker arms, and lifters between cyl #2 and cyl #6, and the backfire remains on cyl #2. I've done a compression check, #2 holds 180, #4 holds 120, and #6 holds 180. It'* been suggested that I may have mixed up a couple pushrods, but being that my compression on #2 is 180, it doesn't look like I bent a valve.

ANY suggestions are welcome, it'* been 3 days and my customer isn't very happy.
Thanks,
Jay