running on two

[cbb]

The fact it is 3&4 rules out electrical as the coils work 1&4 and 2&3.

It sounds like the most likely problem, might be just a bit of sediment picked up from the bowl.

Has the fuel filter ever been changed? If not change it and in the meantime drain the float bowls as it may be enough to fix it.

Put a bit of white toweling under the bowls when draining to see if there is any sediment in them

Will give that a try next Thank you.