Originally posted by David:
If you are going to significantly increase the injector size, I don't think the Apexi is a good solution. It is a fine unit for what it does, and is great for increasing the amount of fuel over the entire curve, but I don't think it will provide the degree of control you will want over the injector pulse duration. The primary problem with really big injectors is getting the car to idle properly. You will need an engine management system (Haltech or Motec) with precise enough control to really dial it down at idle. Otherwise, the car is going to be way, way to rich at idle.
Also, be very careful while tuning your TT car with the new injectors and new engine management system. A few seconds lean at high rpm and you will be shopping for new pistons. Take it to a shop with a Dynojet that has an O2 sniffer, start rich and dial it down slowly into the correct fuel/air ratio. Also, be sure to run fans right into the intercoolers, because the air charge will be colder on the road and you want to compensate for that as much as you can on the dyno.
Just my 2 cents. Hope it helps.