The engine runs great untill it warms up then it starts running rough. It also doesn't have much power going up hills after the engine warms. I am suspecting the problem might be an Oxygen sensor but i think I should ask around before I start throwing parts at it the truck is a 99 and has 160 km on it. Thanks for any help.

 

I would try cleaning tha MAF first. When was it tuned up last?

 

The plugs and wires are good I did them recently and I've tried running the car with the filter out if thats what the MAF is (probly not a good idea) made no difference is there anything I'm overlooking? are there any other possible causes?

 

Look in the 97-03 forum in the FAQ threads. There is a good how to article on cleaing the MAF.