That's a cheap fix. You'd have been really pissed off if you'd paid for a new gearbox and fitting only to find it was exactly the same.

Well done. So it was the MAF all along. Who would have thought it. I know it affects the gearchange, but for it to be so pronounced is a surprise.
I know that when you unplug the MAF, it resorts to default settings in the fuel map. I should have suggested that.

It takes the pressure off trying to find a HP24 gearbox. As you said it is best to change it in the long term particularly if you chip it.
Leave a search running on Ebay to see if one comes up locally. You do see some going for as little as £100 if nobody bids on it.

Believe it or not I actually cleaned the MAF sensor as Dave3d said and it improved the 1 - 2nd lurching upchange and smoothed it out. Two days later worse than ever.

I hope it helps anyone else who has the mysterious loss of power that actually feels like slipping clutches.

Dave I will be chipping it in due course now that all the niggling problems of leaking FIP, leaking #1 injector, leaking spill off pipes, failed MAF sensor, failed in tank pump, failed water pump and failed serpentine belt have been fixed 😆

Dave3d has lent me a spare MAF sensor and now Rommel works with no faults. Thanks Dave3d 👍