Sebring Y-piece (cheaper than Remus, made in the same factory), Remus Revolution with detachable baffle; choose your volume setting. Revolution comes with the necessary 'e' mark for road-legality and gives no hassle with most insurers. Choose from Titanium (light, durable, not very shiny) or Alloy (gives great pleasure to spend an hour with Solvol and achieve a mirror finish).
Run mine without the baffle and I swear that it is quieter than with the baffle.
This should give you a marked improvement in mid-range with no detriment to fuel economy. No change needed to the chip (closed-loop system, so compensates automatically). Check your Throttle Position Sensor while you're at it - mine was set far too low, correct setting makes a big difference to the way the engine picks up and 'blips' on downchanges.
