Originally Posted by 220TC

you can buy 5th injector drivers from Stu at motorsport developments that use the cold start injector. You can program what psi you want it to kick in at and what flow rate you want, I think there about £125

The fuel pressure mod you are talking about is altering the electro magnetic pressure actuator on the side of the metering head, dont do it yourself, take it to somewhere that knows what there doing. Where are you based ?

You will only know whether you need a 5th injector once you have taken the car to a tuner, they will alter the EMPA untill you hit the limit, on mine I could run 17psi before I needed the extra injector.

As long as you have enough fuel and good front mounted intercooler then 18psi should be ok, I ran up to 25psi on my standard bottom end The standard rods are ok up to about 250bhp ish.

Hope this helps, Duncan