I had some cheaper L/t headers on my car and a past tuner filled me in on a bit of info that may be relevant. Kooks headers are the Only equal length header for the s197 chassis. the difference is the exit temps on each cylinder. my exit temps on each cyl. was alllll over the place which scared me once I checked with a temp gun directly off the head. I put the kooks on and my exhaust temps stabilized to within 20 degrees of one another when rechecked but I have yet to get my tune adjusted and check the power level but seat of the paints, oh yeah. I get wheel spin with a lot less effort higher in the gears and I didn't change tube size or collector size. it pulls stronger but I am also built and boosted. this was all due to the equal length of the primaries