A head with a more substantial port & polish + larger valves will make a huge difference when compared to the JCW head.

 

start with an S, since you want a fully built r53 anyways


for those numbers, is obtainable easily, just need some cash and parts. for an r56 you can up the boost to get more power, with the supercharger, only way to up boost is getting a pulley. a 17% pulley will give you the most reliable boost in your car, 19% starts to push the effectiveness of the waterpump. but with the pulley, we don't need a tune. a 17% pulley will give 16-17psi.


youll need a bigvalve head, this requires a lot of work, and when you replace the head, mind as well getting a cam to go inside that. still plenty of options going down this road.


after getting the bigvalve head, youll want the intake manifold ported and the exhaust manifold ported to match this head, way easier if you just got new ones, (OEM intake, and aftermarket exhaust header)


then with all this work, youll definently need new injectors since the stock 330cc will not flow enough fuel. the 380's will be maxed out as well. these will both blow your engine up from being lean. youll want the 440's or the 550's. with the 550's youll be able to run e85.


after all this work, youll also want an intake and a catback (if you have a cat). the stock intake will be choked(unless you drill it out) and the stock catback will choke, plus it doesn't make any sound. having an intake like mine will also give you why many of us R53 owners love our car. its the only whine that ill accept.


with all this done ^ with a potential meth kit, you should see 250+ whp and 200+ wt


as for intercoolers, it still remains the the GP intercooler is the best, but if you run meth, just keep the stock. there is 1 aftermarket intercooler that seems to be good, and that the airtec, not too much information over here about it tho. It looks great. the drawback of intercoolers for our cars is: larger the IC core, slower the throttle response is. the SC only throws out so much air unlike a turbo. but we nearly have the same throttle response as a N/A motor.


Happy searching, this is just the engine mods. theres still lots of aftermarket support for us