spitting and sputtering upon excelleration

I have a 2000 GMC Jimmy SE 6 cylinder, a little over 129,000 miles. The Service Engine light was on for quite a while. I then had a mechanic of mine read the codes. I dont remember all of the numbers but there were 5 digits with a P in front. One was the Crankshaft Position sensor, bank 1, one had to do with the catalytic convertor sensor and the third one I didnt see the code. The service engine light has not come back on. I recently had to take the Jimmy for an emissions test and it passed. Ever since the codes were cleared, it has been "chugging" upon excelleration. It doesnt do it all of the time but seems to happen more often after the truck is hot and has been driven a while.

How do I trouble shoot this?

Thanks!

Liz

check your mass airflow unit, mine felt like there was an increadble hold on the power until after 60 km/h then she got her ponies back it just couldnt climb out of the water till 60