D12 Power Loss 9th and 10th gear

After running with a MBE4000 (Mercedes Benz) on a Colombia for nearly 2 years, I decided to switch back to the engine I once hated 5 years ago: the lovely Volvo D12. Once more, I regain my hate for the D12.

Bought this sucker with a bad egr (d12's and their egr's haha). Bought the egr block kit, pulled out the egr to discover coolant in the pipes (the cooler was bad too!), closed up the egr's, blocked the cooler, finished install. After completing the egr delete successfully, the engine ran smooth. Power, mpg gain, no issues. Everything was oh so perfect. Then about 2 weeks later, out of nowhere we lose power in the final 2 gears. The engine just loses all its power in 9th and 10th. MPG stays at around 6.1 and I pull at max 25k loads. No codes, no explanation.

Possible explanations:
1. We also bought a new turbo boost sensor, pulled old one out (its look like it has been chewed up for years), and installed the new clean one. Now I think that this new sensor may have just quit on us. It happens, faulty Chinese parts. I cannot find out unless I get vcads so this is just on the table.
2. The compute may have de-rated itself, maybe it has noticed something is off (egr) and is now giving off less power.
3. Mechanically bad injector. Maybe an injector is working normally (on the electronic scale) but is not spewing out the correct amount of fuel. Therefore no codes, just less power. Remember its only 9th and 10th, so I do not think this is a real explanation.
4. Fuel Pressure? Why would this be an issue at a higher gear. so this is last on my shortlist.


I should have never bought another Volvo but its too late and here I am. Thanks for everyones help!