I have a 2000 mustang 3.8l and its running bad. I added a cai and some flow master exhaust that did away with o2 sensors and catalyst convertor. Car ran great but then bad. After initial startup car runs great but after a while of driving it loses power and sputters to the point of a slow crawl. Take off is terrible and top speed is around 30 mph. Please use simple terms as I am not a gearhead. Please help