Noonie,
You will want to keep up with your oil changes, and keep your chassis greased. I try to grease mine every 1000 miles. Your brakes will need adjusting on a regular basis as they don't have auto adjusters. If you don't know how long it has been since the brake fluid and antifreeze have been changed, it may be worth changing them. Take a look at your gear oil too.
As to the backfiring and whistling, you might check and see if your vacuum advance is working. The diaphragm might have a hole in it and then you will have a vacuum leak.
Kurt
