Just installed a 355 in my 90 K5. I put a computer cam (RV cam),Edlebrock performer(dual plane) intake, and everything else is basicly...basic. Nothing radical. Well, I get everything in, set the timing and it fires up. But I am only getting 15 in. lbs. of vac. I need 18. I play with the timing some, but end up too advanced. Another problem...won't idle. UP and DOWN. Well, we thought it was the IAC. Well, we put a Holley 670 on it to be able to get an adjustable TPS also. Runs better, but NOW it breaks up at @ 2500 during normal driving, but WOT is fine. Anyone have this problem or know why it would break up? Anything will help. I am at a dead end. One more thing. I set timing at 4 deg TDC. It calls for 0, but with that cam, figured I could advance base timing 4 deg. Thanks...if any other info is needed, I can provide.