I have done some research but didn't quite get an answer. When I start the car, the first 4-5 mins runs horrible! It will stall quite a bit and if I try to drive when itisn't completely warmed up it buck and fart. Could this be ECU related?

 

Its related to the cams. My 280's give me **** when its cold out as well. I just hold it at 2k for a while to warm it up.

 

Even without cams, Evo's take a few minutes to warm up before running smoothly. I let
mine idle a minute or two before taking off.

 

My idle is fine and I have 272s. Runs perfectly... no fuss even in the cold. A warm-up period is always good.

However, I still had my stock BOV (plastic) when I did my dyno pulls and it was leaking very badly and my idle then was very rough. I switched to an Evo IX BOV and it fixed the idle. It also holds much more boost.

You could have a leak somewhere and it's throwing the Airflow sensor off. Try checking all hoses and vacuum lines too.