ooo... fully modded adi... fuhyoo...
what cam duration u use??... if above 272degree, usually u will suffer abit at low end... using adj campulley as well??... if still sluggish (even with aircond off), try get a proper mech with know-how tuning on highcams and so on... highcams, valve/tappet adjustment, campulley and carburetor all need to be configured to work with each other well to get the best out of ur highcams...
misfiring happens when spark occur when ur exhaust valve starts to open... this usually occur when ignition timing is not correct couple with high duration camshaft...
but in some cases such as turbo cars, misfiring is purposely induced to reduce turbolag during deceleration... when air/fuel ignited during the opening of the exhuast valve, the detonation will push the turbine to spin fast even under deceleration... yes, this will damage the turbine in long term... but track cars with time attack in mind wouldnt care much about reliability... all they want is fast lap time...