Aftermarket Header advice and selection

[charley3]

I just ordered a Thorley HDX-634Y header for my 99 XJ 4L. http://www.dougthorley.com/prod-124.htm

I'm having doubts about it for low-end torque abilities because (in hindsight), I'm not qualified to know what header to buy. I should have asked here first. Better late than never.

I need good low-end torque that's at least as good as stock, and I need improvement in mid and high-end rpm performance.

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Bottom line is I need performance increase from 1000 to 3500 rpm, and it'd be nice if performance increased from 1000 to 4000 rpm.

Will the Thorley HDX-634Y be good for that? What header should I have got?

Notes: I already have CAI, 62 mm TB, dent free down pipe, 2.5" cat back.