This is my first time upgrading my R and im trying to way my options in regards to a downpipe or an exhaust system. Now my question is, which upgrade will give the most bang for your buck in terms of performance and sound? Is the "exhaust system" or everything past the downpipe just a sound enhancer or does installing a new ipd or elevate exhaust actually create more usable power? I know a larger downpipe allows the turbo to spool faster and creates less back pressure so then does the exhaust system become the limiting factor in terms of back pressure and the ability for the turbo to spool. Furthermore, I am also thinking of tuning my car to run on 93 octane or in other words a custom tune. So would a tune and new downpipe be the best bang for your buck or tune and exhaust system?