vw polo, starting and flutter problems

[zak321uk]

re: vw polo, P reg 96'- 1.4 se model

i currently own a vw polo, and am having engine problems
have trouble when doing a cold start
get rev counter going up and down, below the number 1 mark on rev counter. engine stalls when braking, after driving 5-10 mins, engine does not stall. have changed fuel filter, and serviced car. still have the same problem. previously used redex in fuel (not sure if that is the problem)

I have been using shell optimax petrol to see if that helps.but still problem persists. any advice or help would be much appreciated.

Thanks!