I just wanted to pass along my experiences with a custom-tuned ECM from Black Bear Performance: http://www.blackbearperformance.com/ Justin Gadberry is the proprietor ans hes a really nice guy. Always answers emails or phone messages. I ordered my unit on a Friday and had in hand the following Friday, even with bad weather on both sides of the country. I don't work for Black Bear, I just wanted to relate how it all worked out. Last week, once I got all my other issues taken care of on my 97, K2500, 5.7L sub (4.10 rear end) with its bad distributor cap, I let it run for a day or so to make sure e\verything was OK with the existing system. OK, everything running perfect, no DTC's, long term fuel trim about -3~-5%. Once I knew thew system was working as it should, I installed the new ECM. HOLY COW! This rig is completely un-constipated now. Juston has the shift points adjusted much better, and I tested both loaded and towing a 5,500lb equipment trailer with absolutely excellent results. If you're traveling say 55mph, and want to pass a car, now the system responds instantly to drop out of OD when you step on the throttle to pass, and you're up to 65~70 without a problem. Before, the response was very "grannied" and mushy, but now it is much, much better. While towing, the rig has a noticeable performance increase - going up a grade that I could only coax 40mph before, with the same trailer and same road I now have just about 50 + mph, and room for more. I haven't yet run a complete tank of gas through it yet so I have yet to see what happened to fuel consumption. I'll post here in a week or so to see what happend. On the stock ECM I was getting right around 15mpg with a mix of mostly freeway and some city driving. Justin offers several options for tuning, and he'll either send you a pre-programmed unit, or he'll send you data logging cables depending on the year of your rig. He also does custom tunes in person. When you go to order he has you fill out an extensive questionerre. NOTE: I've tried other "performance Chips" and tuners and they are, for the most part, prety disappointing. This isn't anything like those. Anyway, I just wanted to pass along that this has been a really, really good experience, and I'm very pleased with the results. 5 out of 5 stars, two big thumbs up!