Orkinman

My 2000 CLK 320 (147,000 miles) engine started making a weird noise that I can only describe as a light putting noise. It kinda sounds like maybe a loose exhaust header maybe? It started after driving home during a rain storm and has been going for almost a month now. It does need a new EGR valve and I'd like to order any parts so I can fix it all at the same time. I know engine noises are tough to solve via forums but I thought this was unique enough someone might know.