I just replaced mine, AC Delco part #2141430. Had rough idle and this fixed my issue. Reason i changed EGR was because, after checking for bad vacuum lines, i looked to see if the EGR was opening n closing and sure enough it was stuck open. Anyways, mines carbureted and i don't have much experience with TBI's but i don't see why this would be such an issue. An EGR valve that is stuck open will make your engine idle rough, Yes. But with it stuck shut it shouldn't affect idle at all. So as long as you can see it opening and closing it should be fine. If you think it's effecting your vacuum advance, hook your vacuum advance to a straight vacuum/non-ported, and see if it runs better. It should run better actually. Using ported vacuum for the advance didn't come around til emissions did. The theory behind using ported vacuum was so at idle/coasting and the timing not advanced it would release some of the burning fuel mixture into the exhaust, hence burning any raw fuel. With todays Catalytic converters, there is really no need to port your vacuum advance. But yea, that's an ongoing argument. If that makes it run better i would set my sights on the vacuum advance. Is your vacuum advance working properly? Is it an adjustable type and adjusted correctly? Adjustable's have a hex head on the front of them. As far as back pressure, i run no CAT, $20 thrush muffler and that's it. So that shouldn't be an issue either.