I have the 5562 kit on my car with a good tune. Putting down about 850 to the ground on 15 pounds of boost with e85. Driving around town on 93 on about 7 pounds of boost it makes a little over 610 to the ground. All stock internals in the motor and I take it 1/4 racing and 1/2 mile drag racing and haven't had a single issue. It's about at that the limit of the stock bottom end, but as long as a good tune is in the car you will be fine. I've got a buddy that's making over 910 with the 6466 set up and a stock bottom with no problems too. Call the guys at Injected Engineering in Kennesaw, GA if you have more questions (they did my installation and tuning and did a great job. Plus they've done a bunch more TT S550's).
I like the elegance of a turbo solution. After all, you're using energy that's otherwise wasted to spin the turbines to stuff more air into your motor so it's inherently more efficient than supercharging. Having built a number of hot rods with turbos and twin turbos, what I don't like is the more complex plumbing and generally more expensive maintenance compared to a bolt on supercharger. Sure, the supercharger causes some parasitic power loss to drive the belt, but it's a LOT less complicated to install, maintain, and troubleshoot.
I'll take the claims that people have been getting 800+hp on the stock bottom end at face value, but I don't think that's going to last for very long. Strength of materials is just a statistics issue. If you stay within the "fat" part of the bell curve that defines power vs failures, you'll likely be OK for a good long while. If you're a standard deviation or two outside of that zone, the probability of roaching the motor is significantly higher. You could go years like that or it could blow up in an hour.
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