The problem here could literally be a thousand different things. You may have a different fuel problem than simply a blocked filter (injectors, pumps etc) or you might even be looking at an electrical or electronic problem with a sensor or computer module. What you need to do is have the vehicle electronically scanned to see if the on-bord computer has logged any problems that will guide the mechanic to the cause.

The other thing you could try would be to run the car on LPG and see what happens. If it runs perfectly on LPG but still struggles on petrol, you’d be very tempted to think the problem is indeed in the petrol fuel system.

EVEN though you're still shy of the mileage for the change, I'm sure you'll find you've exceeded the recommended time, having gone eight years without changing it. Having gone all that time you could probably get away with waiting for the 160,000km to roll around. Any mechanic can make the change. It's not necessary to go to a dealer.