Well before the I got the header i already had 2.5 inch exhaust, no cat and a flowmaster so the header was the finishing touch. Expensive?? well I paid 289.00 for it before shipping, but I wanted it right then and Hawk was the only one who had any in stock (i had been on Calmimi's waiting list for 6 months) The O2 sensor is an easy relocate, I just had to lengthen the wires about a foot. The only complaint that I have is that the collector bolts keep loosening Not enough to make the exhaust leak but enough to make it rattle like crazy I will retighten them (which is only about 3/4 of a turn) and it will start rattling about 20 miles later. Any body got any ideas on what to do about this??