Car backfires and hesitates when cold

I've already done a lot of searches already trying to find an answer, but no luck.

I have a 94GT with 120K miles on it with no internal work done like a cam or heads. All stock other than the Trickflow intake.

When I start it up from a cold start, it runs fine until I put a load on it. The car will backfire and hesitate real bad until it warms up or gets into the higher RPM's. After it has been driven around for a while, it runs perfectly.

I've replaced the spark plugs, cap/rotor, and checked all vacuum lines. Also the timing is set at 10 degrees. The idle has been reset and I cleaned the IAC.

What could this be? Bad IAC? ECT? EGR?

Well, just in case anyone else has this problem, it was a dried up vacuum hose underneath the upper intake. Problem solved!

It's all good. Thanks for the reply. It still has a bit of a flat spot/ hesitation when it's cold and I give it some gas. I'll try bumping up the timing tonight and see if that fixes it. Right now it's at 10*...