i have a '99 5.3 L w/ K&N GENII, Borla Powerset Dual Exhaust, and a HPP3. i was at hypertech's website and they said that the HPP3 works best or is calibrated for stock or near stock trucks (e.g. air intake, exhaust). any more mods that influence air flow like MAF sensor or headers, the HPP3 will require new tuning. has anyone had their HPP3 re-tuned due to additional mods on their truck, and if so, where did you get it done and how much did it cost? i invested $300 on my HPP3 and i hate to spend any more money on additional mods that may make the HPP3 worthless. what additional mods can i do to increase HP without getting the HPP3 re-tuned?