Engine misfire

Good day gentlemen

i have got a carburetor 97 jetta that has a misfire clearly noticeable when started up. If I drive of and is extremely gentle on the gas then the car drives fine as soon as I try to accelerate it misfires again and I have to lift my foot off the gas and put it back very gently after which the car is fine again.
i have changed the plugs and distributer but to no avail. What I also noticed was that if I disconnect the plug leads one by one while idling then there is a drop in rpm every time I remove one exept on cylinder4 were the rpm stays unchanged. What puzzles me is why it runs fine when im gentle on the gas and misfires in the idle. Please can u help

regards
andre