Ok this is a weird one. We have had the special for a long time now, and a few months ago it had an engine change. Is there such thing as a lazy engine? cos compared to what it used to be the acceleration has suddenly become very slow. Ive noticed it happening over the last few months, sometimes I think its just my imagination, but IMO its really sluggish and sloooooowwwww. is there anything that can cause the engine to lose acceleration power over time, or am i just being pedantic?

The accelerator pump on the carb?

My Ami6 was much like this when I bought it, it got to flat out ok, but felt really, really sluggish and took a fair time getting going, I changed the pump and all was well.

Although technically they are all the same, you do seem to get fast engines and those that are plodders. Some are just like that. I guess a lot of it depends on how the engine was run in and treated early on - a barely used 30k miler that has only been to the shops and back may feel so much slower than a 100k miler that is nice and loose for example.

Anyway, things to check include the obvious like the state of the timing and plugs to the no-so-obvious like air leaks, (round carb base or inlet manifold), valve clearances, float level & general carb set-up, whether the throttle is opening fully etc. Try one thing at a time, to eliminate it and hopefully you'll pinpoint it.