I will throw in my real world driving 2-cents in this very long thread I just came across.
My dad and I bought the TAG's back in June 04, $129. 00 each. He has the 12 valve California engine, 1996 model year, 180 HP and I have the 24 valve HO 2003. 5 year, 305 HP.
With his 12 valve engine, it would produce normal black soot and smoke, the soot would accumulate on the body panel where the exhaust exits the pipe. After installing the TAG there is no more soot problem on the panel. There is only a small amount of black smoke when accellerating hard. The other thing it did was pick up one MPG.
With my 24 valve engine, I have no soot or black smoke to begin with, but what I got was a one MPG increase. This was my second mod to the truck and the MPG was instant by dividing miles on trip into gallons to fill back up.
My truck new, 5-03, zero miles.
>First mod when new was to remove the muffler, commute at (70 MPH), 20. 7 MPG avg.
>Second mod, installed TAG, 23K, 6-04, commute at (70 MPH), 21. 7 MPG avg.
>Third mod, installed AFE filter, 24K, 7-04 commute at (70 MPH), 21. 8 MPG avg.
>Forth mod, installed Banks High Ram intake, 55K, 3-06, commute at (70 MPH), 21. 8 avg.
>Fifth mod, installed Moore elm tube, 61K, 3-06, at same time slowed down commute to (68 MPH), 23. 3 MPG avg.
>>>This was my peak MPG of the truck with the old diesel and (68 MPH). <<<
>Around 10-06 in CA is when the ultra low sulfur diesel hit. Mileage droped instantly, as a result and at this time diesel was getting very expensive in CA, I slowed down to (64 MPH) and I got back to my 23 MPG avg.
So to recap, TAG picked up 1 MPG over baseline, the other stuff did not help, ultra low sulfur diesel reduced 2 MPG, slowed down from 68 to 64 and got back the 2 MPG.
"23 MPG, TAG, old diesel, 68 MPH"
"23 MPG, TAG, ULSD, 64 MPH"
I have 101,000 miles on the TAG, and the figure of savings using the numbers before the slowing down numbers, saved 229 gallons in that 101K duration, avg. cost of fuel I set at $2. 90, (03>1. 35 + 08>5. 35 + 09>2. 00 divide by 3 = 2. 90) a gallon X 229 = $665. 00 - $129. 00 for the TAG = $536 gain with using the TAG.