Finally bit the bullet and fitted this.
I've heard nothing but good things about it over the years from people who have actually fitted it to their cars - and a lot of baseless rubbishing from those that dismiss it as a useless gimmick.
It's basically a throttle pedal remapper - www.sprintbooster.com
. I bought mine from profusion customs on ebay for Ł179.99 plus Ł5.99 delivery - took 2 days to arrive.
The car feels like it has more power, and more urgency - it just feels "better" and ties the car together better than the stock throttle map does. You can select between 3 modes - normal and 2 faster programs.
The actual unit is very small - as is the controller unit. The controller comes with 120cm of cable. There is also a double-sided adhesive pad and a cable tie in the package.
Installation was a doddle - literally a 5 minute job.
Added: The seller said this does not affect insurance, but I spoke to my insurer and they increased my premium by 10% - so it's best to make sure.
- - -
Remove key from ignition and wait 5 minutes. Remove the two 13mm nuts to the left of the throttle pedal.
The pedal will now lift off - just be careful of the wires.
Remove the plug from the connector by pressing in the grey clip at the top.
Plug in the sprint booster to the pedal socket, then plug the original socket into the sprint booster.
I found it easier to thread the controller in reverse, so threading the white end behind the steering column, and behind the plastic hook under the dash.
Plug the white clip from the sprint booster control to the white socket on the sprint booster unit.
Then I pushed the cable under the plastic trim next to the transmission tunnel and fixed the controller to the tunnel with the supplied adhesive pad.
Refit the pedal and fasten the two 13mm nuts.
Added: the controller doesn't need to be permanently wired to the main unit - it can be used to set the preferred mode, then disconnected and it will default to this mode when the car is started.
- - -
On starting the car I got a warning about the tyre pressure monitoring not working and traction control being off and the throttle was in limp-home mode.
I restarted and it was all good.
I believe this was due to my pressing the pedal whilst I was doing the install - I've read that this can confuse the car's computer.
One other weird thing is that the led on the controller has a blinking/flashing/strobing faint led when it's supposed to be off. I looked online and this seems to be normal, but it was a bit freaky to see it doing that.