Engine/Transmission (1994 - 1998) Missing when cold

[hsmith]

Just replaced a friends #10 plate with stock, and now until it warms a bit, it will pop, miss around 1500 rpm's. No problem after warm up. Also backed off the afc cause it was smoking pretty good. Still runs good. Not sure of all the mods, as this is a used engine installed by dealer. Any ideas?