please help missfire on my highly tuned pinto

[drifter69]

Hi guys I have a 2l pinto that's now 2.1+ and I have developed a missfire iv changed the coil/plugs/leads has brand new dizzy and electronic ignition any other ideas please share

[drifter69]

Hahaha I know it's the old can u find a problem over the Internet but I'm just after any common things or tricks to sort this it does it under load and Its quite intermittent but starts off up high in the revs then when warm all over the revs

[drifter69]

When power it put down it pulls but as it's building up the revs it it sort of feels like it misses a spark and then catches again and so on
I have had head skimmed
Big valves
Ported
Valve spring seats dropped
Bronze guides
Fr33 kent km
Kent alloy pulley
Bronze spray bar

Block dropped 96.4 bore
2.9 forge pistons
Forge rods
New crank
Basically the whole inside of the engine was brand new built by lowman race engines