You don't explain what kind of noise you are experiencing. Most vehicle
"noise" (RFI actually) comes from the ignition system. In my case, my Ridgeline is VERY quiet ignition wise, but I've done all of the necessary bonding, etc. There is another problem with the Ridgeline you need to know about. If you e-mail me, I'll fill you in.
Further, you didn't state how or where you mounted the antenna, which has some effect on the actual S+N/N ratio. You did state you used a ground strap. A ground strap IS NOT a substitute for a ground plane under the antenna.
There is obviously more to this, so I suggest you visit my web site, and read up.
Also visit the Photo Gallery.