Oh just about 12-15PSI average. 18PSI peak for a split second at the top of the RPM range, right about at the 6500-7K shift points. That's from running a 3.8 pulley on the accessory side. I still have blower belt issues and I'm in the process of getting the wider, 50MM blower cogs w/ a 21/23 ratio. Sooner or later I plan on geting 3.6 and 3.4 pulleys for track use.

The 3800 is a very durable engine. It all comes down to tuning, keeping knock at 0 or close to it and not letting the engine starve for fuel.

 

you can buy an M-90 off ebay for like 400 dollars

 

And that won't do you any good. Unless you plan to get ZZP's L36 SS kit when ever they finally release it.