Really no difference in '99-02 models, '98 had a one year only computer but the sail panel doesn't start bubbling on its own either. Muffler rattling should just be a hanger or the like, that or if it's been replaced and instead of welding it they used clamps they could need readjusted and tightened. Tune-up generally consists of spark plugs, air filter, oil and filter, etc... Fair warning, replacing the spark plugs on a fourth gen would drive a saint to cussing.