Your Fly Lola and Porsche cars must be under performing because their old tyres are hard and not gripping. The 250GTO is not that faster. If your old Fly tyres are hard then get NSR Fly classic supergrips to find the equivalent of fresh Fly tyres.
The easiest way to make a car less boring to drive is to lift up the magnet and place a plastic shim 0.5mm or 1mm under it. Epoxy the magnet to the retaining lugs. Then it is less bogged down by magnetism, far more responsive, and it will have a little more drift around the corners.
Revell 'classic' cars do not have much tyre grip, and nor do Scalextric cars on the whole. Both rely upon magnets only. They will always get hammered by Fly cars if the Fly cars have fresh tyres.
The easiest way to make a car less boring to drive is to lift up the magnet and place a plastic shim 0.5mm or 1mm under it. Epoxy the magnet to the retaining lugs. Then it is less bogged down by magnetism, far more responsive, and it will have a little more drift around the corners.
Revell 'classic' cars do not have much tyre grip, and nor do Scalextric cars on the whole. Both rely upon magnets only. They will always get hammered by Fly cars if the Fly cars have fresh tyres.