If you really need dyno numbers to convince you to buy longtube equal length headers then you shouldn't be buying them. The research has been done. Go over on ls1tech and do some poking around. Someone's dyno numbers are just that. You can't compare your setup to another. For example grab stock ls1 with shorties and then throw on the longtubes and make 5-10 whp over the shorties or you can have a built motor with great flowing heads and intake and a large cam and make 40-50 whp over the shorties. Number variances can even occur between cam profiles. Do your research and determine if the I/H/C setup you are using will benefit from them. Chances are they will but if it's worth the extra 1k is totally up to your budget and setup.