Have you checked the fuel filter ?
I had a similar problem, on part throttle, it would feel like a pulsing, like it's on boost and then not, very quickly. At WOT, it would seem to clear but, I could perceive that the edge was taken off the acceleration. I changed all the consumable ignition parts, I'd alread re-earthed my MAF and fuel pump and had a DIY earth bonding kit fitted. The MAF itself was very clean but, I cleaned it again with isopropyl alcohol and I reinforced the earth for the TPS. I also cleaned all the connectors I could find, again with alcohol.
Took the fuel filter off, let it drain and the fuel was clear as expected. Gave it a blow (against flow) and it felt like a blockage cleared, and all black silt came out. I then washed it out a bit with petrol (sucking it up and blowing it out) re-assembled and the car was as good as new again. I obviously ordered a new filter and it didn't come back (until recently but, again, it was the filter as, I always run the tank a bit low) !
