[Bob Kontak]

Rough strangely because stone cold fires and idles fine. Get it on the road and drive for two minutes and it then it stumbles and does so for five minutes and is fine the rest of the drive. So it's consistent, actually.

It starts stumbling in the middle of cruising as if a switch was flipped.

The EGR valve I'm thinking will open about the time it starts running rough but not sure what could be wrong given how the problem corrects itself.

May be an intake leak but I can spray brake cleaner all over the manifold (when cold) and the fuel trims don't move and no change in RPM. Intake leak would be present at initial start up too or is it so rich then it does not matter in operation?

MAF sensor numbers look ok and are linear upon acceleration and I cleaned some crud off the idle air control valve.

Suggestions? I'm thinking replace the manifold gaskets and clean the EGR system.