eh, the questions were so far beyond my ken that i only listened, but didnt retain much. dealt w/ modifictions that my car is nowhere near.
1) what are the limits of the engine, or head, i think? the answer was that the parts are not tested to limits; they are tested to be sure that they meet X requirement. s2 and s3, for example, take cylinder (pressure) beyond the test amount/requirements, and were tested half as long as regular testing. regular testing is roughly the equivalent of 100K miles.
2) for "longevity" and reliability, aftermarket boost controllers are frowned upon.
3) coilovers are not put on production cars because they dont last as long as struts currently on the srt-4. struts also make less noise while turning the wheel.
4) srt-4 acr adjustable struts for purchase? nah, just buy staged coilovers for the overall better value/deal (price for price)
5) mopar stage 1 springs were designed to keep your control arms properly aligned so that your struts do not bottom out and fail
6) do NOT remove stop rings on struts, they are there for a reason
7) the stop ring, apparently, can easily be removed. the "intent", however, was solely to "slam" the car at a car show; NOT to be driven around on.

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**edit**, now that i see who is responsible for helping design suspension on the car, there is NO way i could doubt that person's claims
goto nats 2006! what up randy!