escort cosworth rally car here is the problem. a few days ago it started smoking heavily then cleared after a short blast. was ran again 2 days later and instantly knocked then cleared and came back again intermitantly with varying severity then afer running at tick over for a few minutes dropped a cylinder and wont pick it up again. the suspect cylinder has good spark but with lots of fuel on and all 4 have good compression.????

any help will be much appreciated as we have a rally coming up in a couple of weeks.

also should add it is mapped and running on sunoco racing fuel