Noice Rough and bucking
 

I have a 98 626 and it has 104k on it. Its been a great car but have had a few problems lately. First had a lound squeel and battery light, chanced altenator and fixed that. Was driveing the other day and it started to run rough when I parked it I heard some noice coming from the engine area. Sounds like its coming from under valve cover or even the timming belt area. When you rev the engine the sound goes away right at 3000rpm and comes back when it drops below right at the same rpm. When you are driveing and give it gas it makes a lound bogging noice as it and will not accelerate when its not bucking. any suggestion.