I set my timing and drove my car (1985 IROC, 383 stroker, HSR, ECM out of a 1990) two weeks ago, it was perfectly fine. No issues at all. Drove it a nice long distance, too.

Today, I started the car and pulled it out of my garage and immediately knew something was wrong. First of all, the exhaust was really loud, like I got a leak someplace. Then, the idle seemed a bit rougher (though the RPM's didn't jump much). Finally, we took the car for a good 50 mile ride and it seemed to be lacking in power.

I have no idea what could have happened in between the last time I pulled it in and shut it off to today. The gas is relatively old, I filled up at the end of last year (in September or October) and added some Sta-bil before putting the car away for the year, not sure if that can be causing some issues or not. I stopped and filled up after about 10 miles and I didn't notice any difference the rest of the way.

I had a previous issue with a rocker coming loose and falling off. Is it possible that one of the exhaust rockers came off? Would that explain the exhaust noise and lack of power? Of course, the two items might not be related but it seems very odd that both would happen while the car was sitting for two weeks. Thanks.