TB42 EFI - Runs rough and backfires

My TB42 runs only on petrol. Suddenly, the engine started to cut off and now it's running rough and backfiring. I have already attempted the following repairs for the issue, but there has been no improvement:
- Changed the coil
- Replaced the distributor cap and leads
- Installed new spark plugs
- Replaced the oil filter
- Had the injectors professionally serviced and tested

Any suggestions would be greatly appreciated.lp

I'm no expert on petrol donks. My train of thought is leading to a timing issue.

You need to check the pressure in the fuel rail.
If the pump is not supplying enough pressure and flow, you'll get rough running and backfire.
Does your Troll run clean if you floor the accelerator? - (ECU full fuel bypass)