Hi guys I really need some help with my VYSS I had a new exhaust put on it and it is surging goes dead while driving it stalls while driving it completely cut out backfires running rich I don’t know what to do I’ve changed coil packs ive changed the plugs, spark plugs, fuel filter also I’ve noticed when I go to refuel there’s no sound when I take off the fuel cap every time I change something it goes fine for a tiny bit then sick again it’s normally good when cold but not when it warms up any information would really help