Need some help here guys. Back story on car, owned about 5 years, had a 2.3 whipple when I bought it with twin GT pumps and 60 lb injectors. Shortly after I bought it I added a Fore hat, dual fpdm's with upgraded harness. Car has run flawless up till I replaced clutch this spring. When I had the exhaust off I had the down pipes and X pipe ceramic coated. After install I ran the car about 20 mi. And I got a CEL. The codes said bad oxygen sensor, one rich and one lean. Car had a slight stumble at 2500 rpm but seemed to run good otherwise. Being a new clutch I didn't run car hard. They were the upstream sensors that showed bad. Car has hi flow cats on it. So I thought maybe I crossed the sensors during install. Switch them and threw a CEL within 10 miles. Went ahead and clean MAF, replaced FRPS and unhooked battery. Also replaced the upstream sensors with new Ford ones. Now when I start car it runs flawless the first 3-4 minutes of idle. Then it drops about two hundred RPM's and runs rough and starts blowing black smoke out of both pipes. No CEL but I've only driven car about 10 miles. Runs good after 2500 rpm stumble. I went ahead and changed the downstream sensors and same thing. I'm wondering if the ceramic coating is causing a higher heat buildup in the exhaust causing the sensors to release more fuel? Out of ideas at this point. I've never messed with my Sct hand held other than look at the parameters to see if there was anything in there to adjust the heat range of the sensors or not and there wasn't. I also started running Torco last year and have about three tanks run through the car. Looking for some advise I really want to enjoy my car again but I'm afraid to even run it in this condition!