Ls3 idle and possible exhaust leak

[Sean1985]

I just finished up a ls3 525hp and a tremec swap in my 67. I probably put about 100 miles on it with no issues. Changed the oil once and it looked great.
A couple days ago I started to hear a light tick and really thought nothing of it. I got on it a little to about 4500rpm in 2nd gear and it got worse. I immediately thought it was a exhaust leak so I swapped the headers gaskets and tightened down the collectors. Still the same.

I found the Evap line was rubbing the idler pulley and it wore a hole in it. So i capped that off and the same thing. The rpm is a little spiratic. Sometimes is stays at 2000 rpm when I start up or if I rev it a little.

At this point I'm a little stumped. No check engine light and I don't have a tool to plug into. Not sure if I need the Evap. The harness does not have a plug for it. Any help would be great. Thanks.