thanks for the reply...the exhaust is not mandrel bent although it is pretty straight with 1 bend of about 70 or so degrees to come out in front of the rear tires. If my memory serves me it's 2 1/4 inch. The headers are tri y's that are small tube, i think less than 1 1/2 inches. How much do you think this could be costing me, and do you think it is the source of the low rpm peak power?