New wetsuit? Major factor. A fresh suit has more inherent buoyancy at first because diving, especially deep diving, simply bursts its bubbles.New BC? Unlikely to have a major effect at this point, but it will become significant as soon as you jump in the water.New weight belt Maybe a nifty new shot belt? Take a moment to make sure the new compares well to the old. Stick 'em on a bathroom scale; often there is considerable variation between claimed and actual weight.New cylinder? Another biggie. Some cylinders are negatively buoyant when full and simply less negative when empty; others sink first and float later.