leedsrhinos126

I've owned the car for 3 weeks now and it's given me nothing but trouble so far.
The parts i've changed so far are
Plugs
Leads
Coil pack
Fuel filter
Also i took the inlet off to check the injector wiring loom etc and everything looked good, no air leaks found either.
The misfire seems to happens under 3k revs so when driving in traffic it's so jerky and i have to put my foot on the clutch to counter act the jerky misfire. Occationally cuts out aswell but very rare.
Any help please as i'm stuck at the minute.
Thanks