Engine: 4.6 V8/hotwire intake/4branch with no cats

I'm having trouble getting good MPG, the guy I've taken it to has replaced the plugs/cap/leads etc... and it's been fully set up, but still getting only 10mpg on petrol, 9mpg on gas he's telling me it's all pointing to the camshaft, but I have got receipts from the last guy I bought it from who only this time last year put in a new short engine/heads/cam and all other new bits all purchased from McDonalds Landrover.

Has anyone had experience with them/the parts they sell?

On cylinders 2 & 6 you can pull the leads off and it makes no discernible difference so it's pointing to the cam

Def west ender said:

On cylinders 2 & 6 you can pull the leads off and it makes no discernible difference so it's pointing to the cam

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Wouldn't this point initially to an electrical fault?

When you pull the leads, is the spark from (say 2) the same as the spark from (say 3) ?

All that's been done, leads swapped then new leads/plugs cap... ...the whole lot, still the same.