i went for the hypertech III tuner, and jet tech support warned me about the 180 deg. t-stat, as some blazer/jimmy's don't get warm enough for the ECU and it thinks it's running cold all the time, which he told me would eat more gas. after i explained it's 75-85 deg here 30% of the time and the rst of the year it's 95-99 with 90% humidity, he said the 180 would be ok. my 4.3 runs at 195-205 most of the time on 87 deg day sitting in traffic jam in south florida. also, the electric fan conversion helped that, cause the fans run steady speed instead of slow at idle like stock. i plan on going to seperate oil and tranny coolers as in deep summer here, in traffic, the hump gets so hot i can't lean my right leg on it. replacing the stock exhaust with a flowmaster cat-back helped alot with the heat, but it still gets hot.
in my personal opinion, not an endorcment, the hypertech was a good choice for me, as it can also read, display and clear dtc's, and you can adjust almost everything you want your way or a pre-set performance way. if ya don't like it, you can change it one or two things at a time, without completely changing the whole bannana. i paid the same amount on ebay for the hypertech III as you paid for the plug in.