Originally Posted by semtex

^No, not past 4k rpm. But up to about 3500 rpm, the lag you're referring to has gotten a little more noticeable. See, I've lost a little low-end torque with these headers. Now, that's to be expected, because the backpressure has been reduced on account of these headers flowing a little more freely. But usually that loss in the low-end is made up for by gains in the rest of the rpm range, hence it's a fair trade off. I have no such gains, at least not any significant ones. My thinking, however, is that it'll be good to have these on when I get a tune, because like I said, I've lost backpressure because these flow more freely. Better flow usually means more room for gains via dyno tuning. I think I'll be glad I installed these in the long run, once I get a tune. Keeping my fingers crossed anyway.