Has anybody compared the performance gains from upgrading the individual portions of the exhaust? Another way of asking the same question is which portion is the most restrictive? Making up numbers here, but: I hear one person say they swapped only the downpipe and gained 25 hp, another deletes the muffler and gains 25 hp. I'm sure that a full exhaust doesn't gain you 50 hp, so where's most the gain? Ignoring sound for now, will I get any more significant gains from a full exhaust than I will from just the downpipe?