1) NOS (£600+)
2) throttle bodies (£1500-£2000 for full set up and RR)
Other than that, go and get a turbo. Converting a c20xe to a c20let is too time consuming and expensive. I've seen some c20let's go for £1000 (engine), so you could do an engine swap. Or ditch your old car and buy a cav/calibra turbo instead, there are few going for £1500 anyway.
did a search-apparently you can get a group n kit from sbd which gives alot more power/torque than chips,and gets rid of the afm.anyone know how much this is?they also do a type a manifold for my cav gsi-is this a good set up.