Had a chip go bad in 05 CTS. Took it to repair shop, they put in a new stock chip and programmed it to stock specs. 2 days after getting it back I am driving around and notice that it will cruise around 70mph and be at +/-2500 rpm but then all of the sudden on a flat road, no pushing on gas or anything will kick up to 3800 rpm. Stays there, even when I slow down to 45mph. I will be driving around on a normal city street with the engine revving at 3800rpm.

On the interstate it does that too and I have gotten in the habit of kicking it into neutral and letting rmps fall way down and then putting it in drive again so it goes back to normal rpms. But it always kicks back up. If I floor it and it kicks up past 5000rpm, it will downshift and go back to 2500, for a little while at least.

Anyone have any idea at all what causing this?

Oh, I just had the oil changed, as always mobile1 full synthetic and I also had the transmission drained and filled 2x. Still does it.