I'm guessing it's your ground to your antenna/antenna mount. A good ground and good antenna placement make all the difference. I've had good results with fiberglass antennas when I grounded it well, but if it's not grounded well, it sounds like crap.
I recently picked up a magnet mount K-30 antenna at Fyling J's, and it sounds as good as any fiberglass antenna I've had, mainly because I can throw it on the top center of my roof, which i the best location in my truck.
http://www.amazon.com/K-30-Magnet-Mount-Stainless-Antenna/dp/B001JZ2V20
You should check it out next time you come over. It's all I recommend anymore. It's so simple to mount and use that it solves 90% of people's CB problems.
It's $25-30, and it doesn't require a mount or adapters, and it comes with a cable. If it hits something, like a tree branch, it just falls over. It's still tunable, which is nice. I have a SWR meter if you'd like to borrow it to tune yours. It's also entirely removable if you want to remove it. I just shut the cable in the door, run it through a sunroof, or out the back window.
I STRONGLY recommend it. Tune it, plug it in, slap it on your roof, and you're good to go.