Flat spot on BMW r1150gs twin spark

Eventually got my bike back on the road after running rough, losing power and cutting out ( faulty fuel pressure regulator valve), but now find that it has flat spot between 3500 and 4000 revs which wasn't there before. Particularly noticeable in 5th and 6th gear. Also plugs white indicating running very lean. The injectors are balanced and tps set at .37 but doesn't stay there varying between .34 and .40. I'm beginning to suspect that in the absence of any air leaks the problem could be the tps unit.
Please, does anyone know whether this would account for the lean running and flat spot or should I be looking else where?

Coil. Mine did just that.

At idle, disconnect the secondary's one at a time. If the bike stops when you disconnect a secondary then that primary isn't working..

Thanks for the reply. Sorry, I should have said that coils, plugs, fuel pump and lambda sensor replaced along with the pressure regulator in last couple of months.