I have an '02 Silverado 2wd ext. I can't decide where to spend my $ this time. The truck has aprox. 125,XXX mi. on it with all the original powertrain other than the cam, diff & carrier, and torque converter. would it be money well spent on say a set of SDPC CNC 5.3 heads, or an intake/throttle body, or should I save that until it's time to rebuild the eng. and adj. fire to the suspension like a 4-link. Would a fuel cell/pump assy. be better? Thanks in advance for any advice.