the xp cam is going to change the powerband and put power in the higher rpms. I wouldn't rev higher than 6300. 6400 is probably too high with your current mods. I have an xp cam with 90 lb valve springs and I don't rev higher than 6300. I am planning on swapping to a set of 130 lb valve springs, intense has a set for sale, and I would venture a guess that zzp is suggesting the 140's because they have no 130's in stock. a lot of people run a 90lb or 105 lb with no problems, but the xp cam will do better with a 130 lb valve spring. the hp/tq curve will be more steady. even with the 130's I don't plan on revving higher than 6300.
