VR running problem

[Doddsy18]

My 1994 VR started running rough, noticed a crack at the back pipe of the left exhaust manifold. That was fine replaced with second hand one. Car still started rough( 5 cyclinders). It does this everytime you start the car after sitting for a long period of time or cool morning air, until the engine heats up and then it runs on all 6. So have changed the leads, spark plugs and put some injector cleaner in petrol. Thought all should be good but NO still running on 5 cyclinders again. Could it be the distributor playing up, sticky lifter or blocked injector or something else? Checked all leads on correct plug sequence heaps of times, not a problem. Can anyone head me in the right direction to fix this it's annoying the crap out me.

[WhiteOx]

Can anyone head me in the right direction to fix this it's annoying the crap out me.

Error codes would be a good starting point.

[XeKToReX]

check injectors, coil packs etc, its either a fuel or spark problem, as for the exhaust manifold crack, i think every VR i've seen with stock manifolds has a crack there.. very common problem..

[VR38]

Have you tried cleaning/checking the PCV valve?