The engine has just been rebuilt and has about 70 miles on it now. It was doing this prior to the rebuild but now it seens to be worse. I am just trying to avoid buying sensors I realy don't need if possible or just get started in the right direction. The engine seems to run good ounce it is warm. I had 1.6 ratio rockers put in, K&N FIPK intake, Ravin muffler, and high flow cat. I also have new ignition wires, cap, rotor, and coil all Accell. Thanks for any ideas you can provide, because I can't seem to get going in the right direction. Also the rebuild included a three angle valve grind, the block was bored .030 over and all new parts were used.