Hesitation, surging and crap mpg.

[Lawrence]

Right, need to get this sorted now. It's got worse recently to the extent that it's hard work getting it past 70, it misfires constantly over 5k and even in neutral at 4k you can hear it's not running right.  It's also drinking fuel, and doing 100 miles/day it's getting expensive.  It's had new filters, plugs, caps, coils, carbs and still runs like a bag of shit. Tps has been checked and is ok. Battery voltage is steady at over 14v (I'll get an exact reading later).

What else can I try? I've got a gallon of petrol and some matches ready which I could try but hesitant to use those yet...

Ta