Hiccups and loss of power

I have a late '84 Rabbit(golf) convertible.  Right after I shift it hiccups, sorta like the pump is picking up air.  This only happens after I've had it on for a while, and the longer it's on the worse it gets.  It'll then start to happen when I press the pedal fast, without any shifting.  eventually getting to the point where it feels more like a clogged fuel filter and I start to worry about stalling out on the road.  I have at this point replaced the fuel pump, fuel filter, cap + rotor, coil, spark plugs and wires.  Heat seems to make a difference bc the other day, right after the sun went down on my way home the air temp also dropped several degrees and by the time i got home it was running better.  That was the day before I put in the new fuel pump.  The fuel level does not seem to make a difference bc it has done this on a full tank, although it might happen more frequently on low levels-not sure.  Turning off the car, even for short periods seems to help some sometimes.  It once was acting pretty bad, I down shifted to make a turn, and suddenly it was better.  WTF!!???  Any Ideas?  I saw a thread about the priming/lift pump in the fuel tank, but someone said they didn't start those until later models.   Tomorrow I'm going to check in the tank.

i would check your timing mate. with a timing gun through the hole in the gearbox

sound like it moved a bit

I have checked that for other reasons, not likely the problem bc then it would be consistent.  thanks though.

Sounds like fuel contamination, causing a momentary loss of pressure.

Not sure if yours has one but if it does my money is on the lift pump.

Fuel starvation under load getting worse as car heats up is prime symtomns of an iffy lift pump.

Might also be worth changing the secondary filter (again if yours has one). This is located above and to the right (if looking at car from rear) of the fuel tank. Its ackward to change while the tank is in place (but do-able) so often gets overlooked.