Start of by cleaning an lubricating the bolt and the hammer/striker, replacing any worn or damages o-rings. If you are using C02 installing an anti-syphon tube in each of yur C02 tanks would help. The burping could be caused by liquid co2 getting into an freezing up your valve. If you need a parts diagram for this marker you can get it from www.kingman.com
If you need details on this go to my post on this thread
If you like spyders buying a new electronic marker like The Imagine would be cheaper, unless you can find upgrade parts used on an auction website.
If you want to up the Compact here are some ideas.
1. Polish the markers internals. Internals being the hammer/striker and the bolt(if you are careful). Use a dremal with a felt bukking polishing wheel and a super fine polishing abrasive.
2. Replace the bolt. I have had good luck with the Shocktech Superfly series of Spyder bolts. It is lighter making the marker slightly more efficient(? did i spell that right????)
3. An expansion chamber is a good part to use. It is a new front grip part that is a sump for liquid C02, that helps keep the liquid out of your valve.
These are just a few ideas that you can use. Otters Custom Paintball webpage has good tutorials of upgrading your spyder.
Good luck and play safe!!!