[leman_opc]

Just a thought - from reading the preturbo injection thread on here I understand the effect on the turbo efficiency in simple words should be that more air mass is pumped by the turbo at same boost pressure.

Now you say your system is MAP based and you expected to see a difference in wastegate solenoid PWM. If my understanding above is correct you wouldn't see any difference as your ECU is boost referenced rather than air mass referenced, so it keeps the boost as desired and simply may not recognise that the air mass and engine torque produced is wrong (higher) due to changed turbo map.

Now, if this guess is true you should see leaner mixture with preturbo injection. Do you have a AFR meter to check? This would be an extremely interesting info....