engine truoble

[Htownsvx]

i just got a new tranny in my car and when it back i was having idaling proble it would jump form 400 rpm to almost 800 rpm. and when i give it gas it is really slow to acc. until it hit 3000rmp and then it take off like normal. and when i turn the a/c is on the problem is worse. i have change the oil, filter and the plug and the check engine light never come on.

does this sound like a ecu problem.
or could it have any thing to do with my two front bad cats?