Polo GT running issues

hi guys,

got my 91 polo GT a few months ago and its been running like a diamond since i got it until tonight, was on my way back from No Rice when it startedto feel like it was missing, at first very mildly, then as the journey went on it just got worse and worse untill i couldnt even pull away from traffic lights without the car stalling and providing me with a disco light set-up on the dashboard!

It will run very rough and extremely rich if i literally just hold my foot on the accelerator up untill about 2000rpm in each gear at which point it does the above. If i dip the clutch it will rev up very reluctantly. The car wont go above about 40mph in 5th gear untill it displays the above symptoms.

Just wondering if anyone else has had this problem with there polo gt, or if anyone knows what it could be??

I was at first thinking maybe the plugs are knackered even though i gave the car a full service around 1500 miles ago, which included air filter, fuel filter, cambelt, oil, spark plugs. The car has only done 61k miles!

Any help would be muchly appreciated as i use the car as a daily runner!

Cheers, Callum.