I recently upgraded my oem exhaust and air filter to a Scorpion Serket exhaust (baffle out) and an MWR air filter on my TS 17. I had a dyno run from before and after, which I already posted in the exhaust section, but am repeating here:
I am quite happy with the upgrade. The objective figures are not that much higher (a few units of torque and power), but the engine is a lot more responsive than before.
It also has an almost flawless air to fuel mixture.
Was considering doing the Hilltop ECU upgrade, but am honestly seriously doubting it now, as I can't imagine feeling a lot more improvement in the responsiveness.
Curve smoothing on a lot of dyno runs makes it very difficult to evaluate the changes.
I'd be interested to know the power and torque increases other users have gotten out of their Hilltop upgrades, to see if it's worth it.