hi, wel iv had my mb6 on ebay, sold it, the guy came to collect her and when he arrived it started to misfire its been a perfect car in the 2 years ive had it and let me down at the last second. the guy did not take it so ive started trying to fix her so i can sell it again so far ive: changed dizzy cap and rota arm cleaned and contineuity tested the ht leads (sorry for spelling lol) cleaned air filter (apexi cone filter) and changed the sparkplugs to bosh super 4s and she is still misfireing, worse when the engine is cold (idle is perfect from start up) but when warm its fine as long as ur gentle, put my foot down and she drops on to 3 again if i ease off the throttle to stick to lets say 40mph then you can feel it kick back on to all 4 again, but try to get to 50 and any more than qwater throttle and its on 3. any help please and i would realy be greatfull as im now out of ideas p.s there is no engine man light on