Originally Posted by trackhead
When people do the low pipe thing, does it change engine tuning or back pressure dynamics at all?
there's a lot of variables in response to your question. ideally, the pipe routing shouldn't make much of an impact on pipe tuning at all. theoretically, a straight pipe with no bends at all in it will be the most efficient at getting exhaust from the valve to the other end of the tailpipe, but if the bends are done without kinks or sharp changes it has been proven that some mighty twisted spaghetti bowls do a fine job as well.
header pipe diameter has a huge impact on tuning - larger headers generally allow better wide open throttle behavior, but usually at the expense of lower rpm power and throttle response. smaller headers, within reason, do the opposite. total length of the pipe also has some impact on tuning, as does how much the pipe widens or constricts at the muffler end of things.
my reasoning for going with a low pipe was purely about looks. if anything, i have lost some power, and am in the midst of jetting it back into the right ballpark.