Exhaust blow Misfire?

[MGB Boy]

My MGB has been misfiring like a bd for the last few days and today when I was under the bonnet with the engine running I found that the exhaust is blowing where the manifold meets the down pipe. Because of this its blowing exhaust gasses straight into the engine bay.

I cant find any other reasons for a misfire, plugs are all clean and gapped, distributor seems dry, plug leads are all on properly and all the wires on the coil are fine.

So before I dig any deeper could the blowing exhaust be causing the misfire?
I'm going back to the garage that fitted the exhaust tomorrow to get it rectified either way.

[Chiswickboy]

You haven't mentioned the points / condenser? Are the points clean and correctly gapped?

If the points are pitted it may be worth changing them plus the condenser.

[MGB Boy]

Checked them today and they seem to be starting to pit so I was going to replace them, just wondering if the exhaust blow on its own could cause a misfire?

[*Al*]

MGB Boy said:

Checked them today and they seem to be starting to pit so I was going to replace them, just wondering if the exhaust blow on its own could cause a misfire?

Highly unlikely, i've heard a car running straight off the manifold and it was loud but not misfiring.