I have a TTI X-pipe in my 3" full exhaust that ends at the rear end housing on my race cars. The "X" ends up at the end of the tailshaft and there is plenty of room to drop the trans pan for service. I had to "ding" the "X" to insure clearance to the driveshaft loop, but it did help performance a bit. The only down-side I can see with the "X" is that I have to drop the exhaust system to change the trans. Gotta watch the straight pipe routing whether you have an "X" or not.