98 jimmy

just got it for free. a couple issues, runs 2200 rpms at 40-45mph untill you lift your foot then it drops to @1600-1800rpms. and there is a flasher that is acting up. sounds like a blinker and quits from time to time(turn signal, brakes, acelleration), and last a high pitch whine from the the exhaust. 160,xxx miles and very clean, so lay the bad news on me or if you have solutions that would be great thanks