I have a 2.8 TBI V6 blazer and I have some things I want to check. First of all what is the operating temperature of the engine ? My temp. meter always shows "150°" ... only when I go on the highway @ 75 miles an hour it raises to somewhere close to 180 - 190° . I have no idea what is should be ?

If this is too low, my high idle ( +/- 1900 rpm ) might be related to this. Altough I am not sure it's the only reason.

This is what happened, while iddling at a normal speed it suddenly without doing anything it raised itselfs to 3000rpm last week. I did check for vacuum leaks, nothing obvious. I cleaned the IAC but it didn't seem very dirty to me.

For now it is lowered to +/- 1500 rpm while driving and when I put it in park our neutral it lowers to 1000 rpm. I also noticed it sometimes takes 10 seconds before the powerbrakes come on when doing a cold start. So maybe still a vacuum problem. Also when I loose the accelerator pedal when going fast or downhill I hear it backfiring in the exhaust. So I think the timing is a bit of also. It also throws a code 33.

Apart from the above it runs fine on both gasoline and propane.