I have a 1991 Blazer 1500. I've been running 35's with 4.56's now for about a year, and as I'm many of yall know, my speedo has been all out of wack. I've been told that to recalibrate it, as well as my tranny, that I need a new ECM. I've looked all over for an ECM for my 91, but like almost every part on the 88-91's, it doesn't exist. Can anyone help me out with this problem. I know I must be doing some damage to my transmission when I'm going 75 mph or faster. Also, I've taken the shell off about a thousand times, and as a result, there is squeaking coming from every corner of the truck. Also, there is a rattle above the driver seat under the plastic that I cannot seem to kill. Has anyone else has problems getting the shell back on to where it is quiet? Any help would be great. I'm currently rebuilding the 91, it was stolen and totally stripped out in AZ last year. If anyone has seen some Gray Cloth bucket seats for my model run, that would be awesome.