I've had this little problem since my PIP stator went out a few weeks ago. And again it was triggered going a constant 70 mph on the highway. KOER showes codes 538: Insufficient RPM change during KOER dynamic response test/ Operator error. This is after I reved it to 5000+ rpms. The car on the highway didn't seem to have the get up and go power it used to have in 5th gear going 70mph. I was hoping after the entire dizzy was replaced with a mint condition used dizzy with a brand new PIP stator installed and cap and rotor too. But it still feels some what down on power, now I don't know if the o2 sensor (it showed up during a KOER test) is being triggered by the other problem (codes 538) or should I just replace the o2 sensor and see if that fixes both problems. I mentioned the code to the divability tech at ford who fixed my pip stator and worn dizzy. He said that codes was probably triggered due to the dizzy being worn out. He showed me my dizzy and it was very worn out, so he gave one he had and just replaced the pip. Low end feels great but top end feels slugish which the o2 could cause this. But the CEL only comes on at 70+ mph and around town (50mph) no CEL and runs perfect. The car has a new fuel filter, fuel pump(255), plugs, wires, cap and rotor, will be running seafoam through in the next week or so. Anyhelp with this code 538 is welcomed and with in the next month both o2 sensors will be replaced they are due. Unfortunatly my internet is somewhat fubared so getting on is somewhat difficult, but I will find a way to read any responses so please leave some if you can. *cough* JT/Grady*cough* :SNSign: