Misfire under load

I have recently purchased a 1964 series 2a 2.25 petrol, I drove it from Maidenhead to Huntingdon at a steady 50 ish no problems at all, since then I have noticed a lack of power under acceleration and now can only do 40 top speed, if I accelerate it coughs, splutters and bucks like a mule. I have changed the following:

Petrol pump, fuel filter, Plugs, points, condensor, plug leads, dizzy cap, rotor arm and still have the problem,

If I keep the speed down then it runs sweet as anything

You didn't change the coil and I would look at the timing / vacuum advance.


Ps
My 1964 2a (petrol) doesn't go much faster than 50.

OOPS! I did change the coil.... forgot to say that, Will have another look at the timing etc, I did spray it with WD40 to make sure verything was moving and it appears to be....

are you running low on fuel and dragging rubish out of the tank?

Try filling the tank right up, may just help

No, just filled the tank up, cleared the filters etc....still the same, its driving me potty!

Could be gunge in the fuel pipes try blowing them back into the tank with a footpump or airline.