01 Impala 3.8L Hesitation stumble
 

01 Impala 3.8L 130,000KM , replaced upper and lower intake gaskets. Full tune up including fuel filter.

We also cleaned throttle body while off the vehicle and some of the sensors too.

Now when first started it would stall, after 2-3 minutes. When it was cold or warm.

If you took it for a drive it would run awsome, but if you were doing around 60-80km and floor it, the car would stumble and hesitate and pause a little while its trying to drive.

I know the computer is relearning, but not sure if that would do it. I let it warm up for around a couple hours and after that seemed to be going good and drive really well too. No stall or hesitation after trying it out on the highway.

Now 2 days later the car is now again, stumble and hesitate and pause once again while on the highway.

The car has no enigne light or codes at all at any time??

Can anybody suggest anything or have had similar problems?

Please help!!!! Thanks