A super charger would be an easier way to get some more HP out of your M52TUB20. Here's a package that available in New Zealand. I'm sure there will be supplier in the UK that offer a similar package.
http://www.trademe.co.nz/motors/car-parts-accessories/bmw/engines/auction-1174041102.htm
The other cheaper options are:
- Fit a M54B25 inlet manifold. You will need an adaptor plate to reuse your throttle body. A M54B30 manifold would have very limited improvement over the M54B25 on a 2.0 L engine.
- Change the VANOS seals to ensure the valve timing is correct
- Fit better designed headers, exhaust and high flow cats, or cat delete (depending on your smog testing laws)
- Clear engine adaptions and drive the car so the DME sets it self up for the engine breathing changes.
- If you really what to, Dyno tune and DME remap to optimise the engine breathing changes you've made and the DISA valve switching point
This will give you an improvement in performance and would provide the right platform for the super charger to fit on top of.
http://www.trademe.co.nz/motors/car-parts-accessories/bmw/engines/auction-1174041102.htm
The other cheaper options are:
- Fit a M54B25 inlet manifold. You will need an adaptor plate to reuse your throttle body. A M54B30 manifold would have very limited improvement over the M54B25 on a 2.0 L engine.
- Change the VANOS seals to ensure the valve timing is correct
- Fit better designed headers, exhaust and high flow cats, or cat delete (depending on your smog testing laws)
- Clear engine adaptions and drive the car so the DME sets it self up for the engine breathing changes.
- If you really what to, Dyno tune and DME remap to optimise the engine breathing changes you've made and the DISA valve switching point
This will give you an improvement in performance and would provide the right platform for the super charger to fit on top of.