Thanks for the tips, guys.
Plugs/wires/etc (ignition stuff have been done recently) except coil.
My car seems to run rich all the time but performance is good when cold.
When warm, there is hesitation on acceleration and idle becomes lumpy.
Disconnecting the EHA seems to have got me better mileage but need to drive further to be sure.
Fuel indicator was at 3/4 mark with only 50km on the tripmeter when I first noticed this problem on Saturday with the EHA on.
I topped up the tank and took off the EHA yesterday.
Today, having done 70km, the fuel indicator is still above the 3/4 mark.
Trex - I'm not losing fuel from a leak - performance is crappy and exhaust is smoking black (sign of a rich mixture).
Keep 'em coming guys.