Ive been on the same boat for years, itching for power but nothing out there for the aph, and always mad at myself for not jumping on the apr stage 3 kit when they were making the software and was available.
from what i have gathered recently is that the best way to get the aph to maximum potential, you need to first do a wideband ecu conversion. the aph is a narrowband ecu. Not sure how this conversion is done but you need 2002+ ecu and corresponding engine harness and whatever else is involved, different 02 sensors i think.
once you get the car running correctly with a wideband ecu, you can take it to the next step and go big turbo just like you would in a jetta or gti
there are plenty of places that sell parts
atpturbo.com
stpturbo.com
pagparts.com
for big turbo software, unitronic seems to be the company that they use the most. $900 chip
i too have been contemplating myself of just droping in a k04 but for the price im not sure its worth it in the end.
you dont need bigger injectors for k04, but i believe you need a different TIP, to extract maximum power from a k04 you need corresponding software and that can quickly add up
SMIC---tyrolsport.com makes it for the beetle, heard good things about it, never had it in my car
If you trully want to go big turbo with the aph, you need to go the extra mile it seems and thats probably in the 5-10k range once its said and done.
Im interested to see where you go with this as i'm thinking to tackle the engine next
my engine mods have been on hold for a while because i dont know which way to go.
giac 93 chip, 4bar fpr, forge dv, dss level 1 axles, ecs stage 1 clutch. neuspeed p-flo, jetex 2.5 catback exhaust (stock downpipe )