850 T5R momentary cut out under hard acceleration

[PSJVTHEBEST]

Any help will be greatly appreciated!
Much already done recently when she wouldn't start at all or ran very badly including:
- New MAF sensor
- All new vacuum hoses
- New distributor cap and rotor arm
- New plugs and leads
- New O2 sensor (Bosch) – there’s only one pre-cat
- New fuel pump
- Checked fuel pressure now and c. 40 psi – ok
- Cleaned and serviced injectors (new seals and filters)
- Changed oil, filter and air filter
- new crankshaft position sensor
- new camshaft position sensor
- new radiator
She runs really well now and the problem manifests only under hard acceleration in sport mode when I kick down, revs are above, say 3500 to 4000. It's like I have hit the brakes - it does it 2 or 3 times, the gearbox then shifts up and revs drop and all is good again with strong turbo boost.
Checked the codes and I have got:
A3 (ABS)
142 Faulty brake pedal switch, open or short
424 Pressure switch for TRACS, faulty or short circuit

A7 (Combined Instrument (Trip Computer))
122 Temp. sensor interval too long

The A3 codes may be historic from when I took off and cleaned the brake pedal switch during re-commissioning as it was faulty. Could there be a link or are these faults probable 'red herrings'?

As I said, any help will be greatly appreciated (and apologies for the long post!

Pete