jameswf

Hi, I have a 2013 Petrol 1.2 TSI Octavia, it's currently just under 70k miles, and had a full service back in April or May. For about the past 2 months, since I've been doing more motorway driving after starting a new job, I've noticed on several occasions that when I go over like 75mph that it feels as if the brakes are being softly pressed and the car will slow down by approx 10mph to 65mph for eg. There is NO warning light that comes up on the dash. It then speeds back up again. Ive noticed it tends to happen more when it's either rained or is raining? Father in laws mechanic friend asked when the fuel filter was last changed, but after some research I'm under the impression that it isn't possible to change on tsi engines? If that is correct? I've put a bottle of redex in, which doesn't seem to of done anything. I did wonder if it was from using e10 fuel, so I've tried e5 fuel but it is still happening. Any thoughts what might be causing this problem?