MG ZT 190 running problems, any advice?

Hello all,



Had my 2004 ZT for a while now but I have never been happy with the performance. The top half of the rev range is full of flat spots and recently I timed my 0-60 which was over 10 seconds.



Low down seems ok with a definite pull at around 3000rpm when the power vis opens. I recently replaced the balance vis and whilst the upper rev range has improved slightly there are still flat spots and once the revs reach 6000 rpm the car appears to hit a brick wall and really refuses to rev higher. Air filter was replaced a few months back and I've tried cleaning the inlet manifold with carb cleaner (though it was pretty clean in there).



My local specialist has taken a look and ran diagnostics but can't find any fault codes. They seem to think it might be the case that the timing is out. Whilst this might be possible, I had the belts changed by an MG specialist (found on this forum) six months ago and they have assured me they use the correct MG/Rover cam locking tools so the timing can't be out.



I've spent a lot on this car last six months so I would loathe to spend more money at my local specialist for them to try and diagnose the issue. Does anyone have any diy options/troubleshooting suggestions I can try myself to try and find what the problem is?



Thanks

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