X3 on the Hedman Elite headers. I combined them with a huge Magnaflow dual 2.5" in - single 3" out placed between the headers & the stock catalytic converter. They were no louder than stock & sounded MUCH nicer. A bolt came loose on the first trip out creating an exhaust leak, but replacing the gasket with one of better quality fixed that.
The installer talked me into replacing the old plug wires with standard straight boot plug wires. One of them burned through on a trip to Seattle & I ran the last 75 miles or so on 7 cylinders. Not fun. I went to the local parts store, bought the Accel universal right angle boot wires that are in pretty much every parts store, installed them, & had no more problems.
I've had them on for 8 or 9 years since then with no problems. I do recommend using better quality gaskets than what the headers come with and changing over to right angle boot plug wires, for obvious reasons.