hesitation after starting

hi all,

I have a 91 2600i and it starts fine. When I give it gas, at a certain rpm it starts dropping out every couple of seconds like it's being revved. If I give it alot of gas, it will get passed it and run fine, but as soon as I let off and get it to that magical rpm, it starts doing it again. Once it's warm it runs better, so I'm guessing it's something with the cold start valve or something similar. Does anyone know for sure? And where is it? My book doesn't mention it.

Thanks!
Alan

pretty much the only thing i ever see go wrong with 2600i if every thing else checks out. is the ecu/pcm is bad tough to pimpoint and expensive.