Turbo 07 GT
 

How many miles is too many miles to add a turbo kit

Mileage isn't the issue. Do compression and leak down tests on each cylinder. If the compression values are even across the board and the leak down is low, you have a good healthy engine.

Brenspeed did some videos on youtube. They bought a high mileage stand 2007 with a 110,000 miles. It was a clean car and they did a variety of bolt ons and made 350hp. I don't think they added a power adder but like the poster stated above check compression. I think that shop did a high mile coyote build as well. They took the cars to the strip and raced. They hold up fine.

My car
 

My 07 mustang gt is a five speed with a mcloed stage 2 clutch a variety of bolt ons and the Mutha Thumpr cams and it makes 385 hp i am wanting to turbo it. My compression it the same acceoss the board with minimal leak. How much boost with the propper tuning can i get out of the stock block before i need a stronger one

Is that at the crank or at the rear wheels? If it's at the crank (more likely), how much rwhp did your car put down?

My car
 

07 NIGHTMARE, If your stock block checks out, like Deno said, I would start at 6-9.5 boost. Now remember, there is a ton of other upgrades that must be done if you go above the 6-9.5 boost, ie cams,injectors, added cooling, etc. Now, if your 4.6 has been properly upgraded, and prepared for the turbo, I would not go over 14 psi of boost.