I've got an 87 turbo wagon with a pretty tight motor. I run mobil one and have never had any cooling problems. i was wondering what's the max rpm's to pull SAFELY for extended periods of time. When i cruise about 60 mph, my vacuum is about 9 in. , but when i cruise at 70 it jumps to about 11 in. 70 is also about 3500. Does anyone else get about the same vacuum readings and how fast does everyone else cruise.

Sounds like you have an Automatic. Typical rpms for one.

I think 70mph is ok for cruising and it keeps the motor in its powerband. If you want to change the rpm's, change your wheels to 14in Pugs, it helps alot without drastic drivetrain changes/swaps.

Actually i have a 5 speed. I'm running 175/80 13's right now. I also have some 185/80 13 snow tires but they seem to bog the motor down.

IF you have a GOOD turbo, you SHOULD be showing BOOST while cruising

If 13in tires are bogging your motor down, then theres something going on that isnt right. I have 14's on my 86 turbo wagon and it only bogs if I put it in 5th gear to soon.