[Excaliber]

Sounds like ignition to me. Heres the clue: Replaced cap, rotor, plugs etc and all was fine for awhile. With BRAND new components AND a 'weak spark' there would 'just enough' spark to make things work OK. But as soon as the new components start to get worn in, the spark plug threshold voltage drops to low and once again causes a 'weak spark' condition.

I'd check the coil and the ignition 'box' that fires the coil. As well as primary voltage to the coil\box.

Again, overall your symptoms sound more electrical than fuel related, with spark being a prime suspect. Generally speaking the FIRST question to ask and needs to be answered is:
Is the problem FUEL or SPARK? A weak spark will leave the plugs fouled, maybe wet, leading one to the WRONG conclusion of a 'rich mixture', for instance. Diagnostics, as much 'art' as it is 'science'.