I have worked with performance cars and motorcycles for most 40 years, and my father's garage had a sign on the office wall that said "Speed costs money--how fast do you want to go?" When I spend hard-earned cash on my vehicle I want to know how much real bang I'm getting for my buck. I appreciate the opinions of other owners, but I'm also familiar with what I call the "gold factor"--the more gold an owner spends on a modification, the more he wants to believe that it works. No butt-dyno for me--I want some real evidence.
A short note here on dyno testing. I never compare dyno numbers from one testing center to another; there are too many variables between machines, operators and conditions. I prefer to keep the variables to a minimum so I test on a good-quality, calibrated machine manned by the same operator for each test. Temperature, humidity, and barometric pressure can cause variations in readings, so I always use a machine in a climate-controlled environment. I am fortunate to be located near Colvin Automotive in Austin, Texas; they feature a Dynojet 248 chassis dynamometer that meets all of my requirements. Expertly manned by Daniel, their machine should provide consistent and accurate readings to measure the effectiveness of future mods. This shop was recently featured on an episode of "Overhaulin" on The Learning Channel when they helped to build and test a beautiful 1970 GTO for Lance Armstrong.
I made a number of modifications to my 2005 Frontier (with essentially the same 4.0 engine as my 2012 Frontier) and posted a description and dyno test for each one. Hopefully, other Frontier owners will benefit from my successes and failures. For dyno charts and results, see the links below or check out the modifications page.
Dyno Day 1 (setting baseline)
Dyno Day 1 (testing K&N filter)
Dyno Day 2 (testing premium fuel)
Dyno Day 3 (testing Gibson cat-back exhaust system)
Dyno Day 4 (testing aFe intake)