I am in this thread suggesting to do an M62 top swap. This will keep the engine completely Series 1 except for the throttle body, though that can be kept with a bit of tinkering. The only Series 2 stuff would be to change the PCM so that pretty much anyone can tune the car.
PRJ can do great things for a 16/17 yo guy, and it should only cost $75-100 to tune this specific setup because I imagine it would take 2-3 hours. Because of the 8:1 compression, different injectors, and different boost for the RPM range, the tune actually would very slightly vary from stock. This is because Series 2 sensors will be used.
The PCM uses 4 sensors for tuning & such: IAT, MAF, MAP, and O2. IAT is a temp sensor. MAF is taken directly from a Series 2. MAP is taken directly from a Series 2 and bolts straight on. The O2 sensors may be interchangeable, but in case they're not, the Series 2 sensor threads right into the place of the old one. All other stuff stays the same unless certain items like the coolant temp sensor & oil pressure sending unit are different. IIRC, they're NPT and are interchangeable.
94 STEi and 99 SLO