Im having poblems with the motor running rough, well sometimes its lovely other times dreadfull.

Im running a 2.0 ZVH with MFI about 200bhp.

When driving it can be slow or fast but more frequent when going faster.
the car will be fine then all of a sudden it like the car hesitates. If i put my foot flat down te speed doesnt increase and the exhaust makes a kinda gurgle bubbling noise.
If i take my foot off the gas and put it back down i get a loud pop a miss fire i guess. But if i keep my foot on the gas eventually it stops the problem and carrys on as per normal with normal speed increase.

i have changed the HT leads for motorsport ones. Changed the distributor cap and rotar. Also put denso ik27 plugs in with a 0.7 gap.

Please help. seems like when i fix a problem i get another