Surging/won't idle
 

I had my LS1 tuned and ran fine in my 78. Now it's in my 70, it surges and don't idle. I did change the headers to a different brand, but same size and a SLP 25% to a ATI 10%. Would this be enough change to cause this problem? The ECM was disconnected for about 6 months.

Just tried to check for obvious leaks, didn't see any. I did disconnect the IAC and the surge went away.