gas tank

I bought this tank online intending to stripped and repainted. I've decided not to take on the project. The tank is in excellent condition. There's a couple scratches in the paint, but if getting stripped no big deal. No dents. I had removed the side pieces, but the they can be reinstalled...

Recently, since my second service a few hundred miles ago, I've noticed when filling up that the vacuum inside the tank is much stronger than I ever remember it being before... When out at the weekend, it was so strong I actually struggled to get my petrol cap open and thought the lock had...