Over boost problem

Hi all

Can anybody help as I am at my wits end.

My problem is with my Mark one Skoda Octavia Vrs 1.8t ( 180bhp).

When I put the throttle pedal to the floor turbo makes all the noises but no power,TC lamp comes on.Sounds like turbo is dumping the boost.

Fault code read is max boost pressure exceeded ,MAF sensor above threshold.

So far what I have done.

New MAF sensor

Belled out MAF wires to ECM all good,checked voltage 12v on blue,5v at red/purple

New N75 valve

New turbo actuator

New dump valve

New Y pipe and nearly all turbo pipes changed

Other pipes checked also for leaks

Re-set ECM to factory mode via 00000 coding

New spark plugs

New coil packs

Air filter replaced

Tired of throwing money at this fault,been told could be throttle body but again the cost.

Any ideas would be much appreciated,or if anybody could recommend a tune specialist in the Redditch are.