A note to all Gadgetmen- A G-Man who has not yet posted here, but who has had great success on his own GMC Sonoma 4.3L V6 with the Groove, just told me of a problem he just fixed on it. He's Grooved it, used MPG Remedy, and got a substantial gain in power and MPG's. He just told me he found an air leak in the area of the air filter housing or duct. The Sonoma had lost some of it's gains, so he looked and found a bad O-ring seal on or in the area of the air filter housing, his words were "I replaced that O ring and the thing just came alive!"
I've asked him to send me a pic of this O ring. Any significant air leak in the air inlet duct, or area of air cleaner housing, or Mass Air Flow (MAF) Sensor can upset things, skewing MAF sensor data to ECU. IF the air leak is bad enough, the engine won't run, or can stall out! Or, as in this GMC's case, can run worse, must have been a fairly small air leak??
So while I'm waiting for him to send me a pic, (he's currently working insane hours) I wanted to call this issue out to everyone. A small leak in the air inlet system is easy to miss, the engine may run, but not to it's potential! Check integrity of the entire air inlet system, upstream from the throttle body.