Not enough back pressure is a myth. The ideal situation would be to have no back pressure. Where this gets a little trick is the headers. If the primary tubes on the headers are to large the exhaust pulses do not create a vacuum behind them to promote scavenging. So...If the primaries on your headers must be the correct diameter so that a vacuum is created, but no back pressure in front of the exhaust pulse.
No more trucks, but this is what I used to have. 2000 GMC Sierra, 6.0L-LQ4, Built 4L60, LS6 Cam, The Other Guys Headers, 3 inch exhaust and 7 chamber flowmaster, 43lb injectors, Nelson Tuning, Drop - 3/4 McGaughys Spindles, Bell Tech Shackles & Hangers. Best time 13.59 @ 106
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