www.boxertrix.com

Had what seemed almost identical issue with one I had that had been stood for a long time with old petrol, managed to sort it with fresh petrol and a good long run. try it its the cheap option...before you go down the injector, fuel filter, etc etc etc road.

Try new plugs and ride the full tank dry after adding some petrol Reddex.
Failing that, make sure there are no mice nesting on the air filter.

If the throttle bodies are so out of sync and the fuel filter hasn't been changed I wouldn't particularly trust that the valve clearances have been done. Best to check them the rebalance the throttle bodies again.

Fuel filter, fresh fuel and an 'Italian tune-up' - usually sorts a multitude of issues.

Two or four plug? Could be coil pack if four plug. Could be spark plugs if not.

Let's see if i have this right

Your running plastic fuel filters with the paper filter material inside one to either side they have been filled with crud you reversed the fuel flow to clean them

You are not running the in tank filter that keeps the crap out of the fuel pump


So you have a fuel pump full of crap fuel filters that have been full of crap and will still be blocked as you can't clean them out they are disposable once the paper becomes contaminated that's your lot

Try replacing the in tank filter and possibly the fuel pump as that's likely to be goosed now before trying anything else

Edit
If I'm wrong try setting the TPS

Well done on finding replacement injectors
Were they much cheaper?

We are off on holiday for a week i will be looking at these when we get back keep us informed as to how they work out