cisurfer

I have a 2002 gt with tons of mods done and lots of replacement parts. It has 130k on it and isnt my DD anymore. When i start it and until it warms up (after 5-10) mins when I give it gas while it's sitting it stumbles a bit and if I hold the rpms steady it has a slight sparactic miss. What could be causing this? I doubt it would be head gaskets because of no coolant missing or burning. Piston rings? It only does it when cold