Last time I posted here I was looking for a Delorean, and about 3 months ago I purchased 3455, Stainless Bullet's twin turbo. So far my weekend projects have been manageable and I've found a lot of good advice here in the forums. I've replaced the passenger side window motor, rebuilt the mode switch, replaced the alternator and cleaned up some electrical connections, fixed the dome light and engine compartment light switch, recharged the AC, and replaced the injectors and plugs. She was running great after updating the alternator, until this Saturday when I noticed a line to the vacuum advance was unplugged. I plugged it back in and noticed the idle was a little smoother and the boost gauge (which hasn't moved since I bought it) now reads 20 psi of vacuum and actually responds while driving. I also noticed an intermittent sputter from the passenger side exhaust. I disconnected the vacuum again and the sputter went away. With the vacuum connected, it seems there's no sputter when the engine is cold and it comes back when it's warm.

I've been reading up on possible causes, and came across the dollar bill test. I tried it and sure enough the sputter corresponds with a sucking from the exhaust. I'm guessing this means a sticky exhaust valve at worst. I pulled the plugs, they look clean and gaps are good. Just to rule them out, I ordered some new plug wires.

I'm looking for suggestions or advice if I'm barking up the wrong tree. I'll post a video tonight. I should add that I hear the sputter at idle, but not while throttled. It's most pronounced when throttling down and when turning off the car...you can see for yourselves in the video.

Worth knowing - there are no mufflers, and the O2 sensor is not installed, so any other idle issues may be related to that. It looks like it was cut out at some point and the hole in the bung was patched. I ziptied it to the frame until I can get it repaired since it was hanging loose...I guess while I'm asking questions, is that a problem or should I just disconnect it altogether? I have an AF gauge installed as well, but I'm not sure if it's accurate...it has never moved from rich.