Hello first post on this forum. I don't like to start off this way but here goes. I just purchased a 2001 Blazer 2 door LS. I bought it knowing it was flaring the 2-3 shift under part throttle, I rebuild these transmissions so not a problem. The problem I am having is I do not believe it is in the trans. I forgot to plug in my maf and iat sensors after replacing the washer pump and the transmission shifts fine. This made me think that maybe it needed a new maf and iat, I have since replaced them along with tps and ect sensor. I also replaced the fuel filter and air filter do to hard starting when cold. I also replaced the force motor and installed a bigger boost valve in the trans. I can shift it manually and it will shift just fine. It will also shift fine under wot. Also when I shift it into OD or any forward gear it hesitates like it is low on fluid, I have checked the fluid. I believe something is effecting line pressure which is why I replaced the force motor and boost valve. I have not replaced the map sensor yet which is my next step. I can almost drive it normal if I let off the throttle once it starts to flare. Again if I unplug the maf and iat together it will shift just fine through all gears with a nice positive shift. It will also shift fine under wot 99% of the time. I have noticed the ECM has been replaced but looks like it has been flashed to the vin. I am having a hard start when it is cold and after it sits for a couple hours as well. I am thinking fuel spider and reg first, then fuel pump. I have tried priming it first and it does not seem to help, also no gas smell in oil. I do not know if these 2 problems are related? Sorry for the novel I am just at a loss here. I think I put everything in that I know of as far as describing the problems. Thanks for any help.