I have a '95 355 with cat bypass/tubi installed. Car has run like a top until recently. On a long trip back from Foxwoods to Boston, car all of a sudden throws a Check engine light and loses power. The exaust changed its note and sounded sick. after a few miles check engine light stays on but sick exaust nose goes away and power returns to normal. its a problem that comes and goes frequently. car runs fine about 95% time and sounds sick + down on power the other 5%. The other thing is that the slow down light comes on but I do not have any cats??? the only thing I can think of is the addition of BMC filters about 1 month ago. The car ran fine for the first 2 weeks with them installed.