To start with, a Ficht engine has not got adjustable oiling, apart from initiating a new brake-in cycle.
First test the compression. Cylinder 5-6 (The bottom ones each side) has less compression than the rest. This is done on purpose.
Did you check the indexing when you refitted the plugs? Is the sooty plug dead?
A vacuum gauge and a bit of clear hose on the fuel intake side will show if there is a supply problem. Max 4"HG and no air bubbles. Use only 3/8" fuel lines and primer.
Check the exhaust back pressure fitting to the EMM. It is often clogged.
Last, you need to connect a laptop and test at high speed. A drop test can be done for both spark and injectors and will show up problems easily.
My guess is fuel supply.