I have been trying to figure this out for some time now, but I am stumped. Sometimes when I am driving my tracker, it lacks power and I have to floor it to get it to do the speed limit, and down shifting into 4th or 3rd doesnt help. I have been noticing that if I have it stopped, and rev the motor from 1/4 to 3/4 throttle, it will puff black smoke(almost as bad as a diesel). It used to make oil smoke when I hit the gas after it was idling for a while or after I use compression braking to go down a steep hill, but a new pcv valve fixed that. I dont know what is causing it to run rough and hesitate and lack power sometimes, while other times it has plenty of power. Another problem I have been having is that it likes to idle high and sometimes surge when I turn on the lights or the heater fan or both(electrical load). I was wondering if anyone has any suggestions as to what can be causing these things to happen(I am mainly wondering about the lack of power one) and if they could be caused by one thing. I replaced the oxygen sensor about 9 months ago, and it has new spark plugs.