Use Automatic Transmission Fluid to lube your airguns. It works great and doesn't rot the seals and o-rings. I've been using it for years in all my paintball guns and pellet guns. Pelgun oil is basically just ATF. It works great and hasn't ever given me any issues. It's also prone not to detonate, since Tranny fluid is put under loads of pressure in it's intended application. A one quart bottle will last you for a long, long time! I prefer Castrol synthetic ATF for lubing airguns personally
Be sure you get plain-jane ATF, the less detergents, the better
I also have a 1377. As stated, the barrel bands tend to loosen up, and the barrel will shift, especially on newer models. Some folks do make aftermarket bands, though.
Also, you may need a new pump cup, they tend to deteriorate if not maintained, and it may be the source of your power problems. you can just order a new pump cup from Crosman and install it. Be sure to store your pellet gun with 1 or 2 pumps of air in it, this will help maintain the seals, and the gun will last years longer, and operate more consistently in the long run. if you store it without air in it, the seals tend to warp over time, and won't be able to maintain a good seal.
-Speed is a question of money; How fast do you want to go?