Tim I'm going through the same thing with my 2000 '31 Sonic. I have 454 MAG MPIs and need manifolds on one engine and the other will need it soon (Just starting to rust). I'm interested to see what you found. I have the Corsa Silent Choice and would like to keep it. I understand some manifolds won't work with the Silent Choice.

I put stock manifolds on the engine that required it for now but my winter project is going to be to find a good set of manifolds and risers that will work with Silent Choice and give a boost of performance.

Any ideas?

I used stainless marine for some 454's with silent choice and it made a big difference, put some stainless marine on twin 502 and only gained mid range accel, I still have 1 set of good stock manifolds if someone needs them(cheap)