Back when I used to drive to the Shootout, it was 850 miles each way and took me about 3 tanks each way, I could get about 280-300 miles per tank. So ~25ish mpg doing 75-80mph for hours on end. Not bad for a car that was making 450whp at the time.
Maintenance and tuning first, there's a lot left on the table in the stock tune. Make sure to get a good wideband, not glowshift. I've seen their boost gauges be 5 psi off, so clearly quality is not superb.Also keep the boost solenoid as it can be used for electronic boost control through Ecmlink.
If you need bearings it would be almost certainly due to an oil pump failure, at which case the whole block needs to be cleaned and gone through. Was there glitter in the oil pan or something that gave you that idea? If there is no oil pump failure then it's a 99% chance the bearings are...
If I'm not mistaken the T25 needs to be balanced on a VSR balancer as a complete unit, make sure the shop has one, usually makes them not worth repairing.
Share a log with us to look over, 109mph is def not ideal for a red, even on pump gas. In my experience, you'll make more usable power with lower timing and higher boost.