I agree 100% with the custom tune. I bought a Jet programmer for my 97 from Summit. It does help, but for the same money I could have had a custom tune. The plus to have the programmer, is that it is also a live sensor reader, and I can reset any ECM codes. I thought when I got the programmer, it would make a lot bigger difference than it did, but it did help some. The biggest difference I see is in the transmission. It shifts a lot crisper than the long slow shifts before. The way I gauge my truck is, when I turn right out of my street, and I get straight from the turn, then floor it, I was doing 50 MPH at the first block. After the programming the truck, I now do 54 MPH. Also I fixed the speedo being off, and did away with the speed limiter. The truck now limits out at 228 MPH, not that it will ever go that fast. My truck is set on max performance, for premium fuel, but I still run regular with no issues. I tried premium first, then plus then regular. Non of that made any difference in my truck. The ECM reader and live sensor reader has come in very handy in finding issues with tripped ECM codes, and looking at what the sensors are doing with the truck running. All in all I am happy with my Jet programmer. If I ever get a custom tune, I would keet the programmer, because of all the things it can do with the live sensor readings.