i put a 1990 tbi 350 in an 1992 s10 blazer about a year ago and everything has been fine till recently. since a few days ago it idles at about 1700rpm all the time, it wont start when its cold unless you step on the gas. something is making it dump gas into it because it runs real rich & my gas milage has been cut in half. the temp guage goes from 0 degrees to 260 in about 10 minutes, and there is no way the truck is running that hot. it also wont shift into overdrive no matter how fast you go. and the last thing is if your sitting with it in gear holding the brake, the speedometer goes nuts. (it has the digital dash) it jumps around all numbers. can all these be related? ive been told it coluld have something to do with the temp switch? im kinda lost... any help would be appreciated... thanks alot