[ainarssems]

I did think of Nitrous oxide and while it is fairly inexpensive to install the usage costs are too high.

So I looked at alternative. You could use compressor part of turbo hooked up to electric motor to give you on demand boost. Initial outlay will probably be higher but running costs very little. It is a while since I looked at it so things may have improved now. but I seem to remember that about £750 investment would give you 50% more power for 2 minutes with 30 minute re-charge time with which is compareable to 11lb NO2 bottle at about £50 for the same 2 minutes of boost.