Buzzing/Humming Sound

My Bmw is running pretty good. One exception is that when I'm driving I hear a slight buzzing or Humming sound. It reacts louder or quieter when I play with the gas pedal. Could this be a exhaust leak somewhere? I know I was told I need a new muffler, which to me it's not loud and also I was told I need a air intake boot due to cracking. Also has anyone let a mechanic do a motor vac, and did it help your e30? Thanks guys.

most probably the in tank fuel pump. Mine does it all the time. Might be on its way out.

mines new and it makes that noise...but i dont have back seats so thats probably why i can hear it.

let the bee out of the muffler. if youre talking about the 86 in mein auto, and if it varies with playing with the pedal, the first thing i would check is the vabration dampner. this is after the in line fuel pump, about 12 inches forward and 8 inches in from the drivers side rear tire. it looks like a pressure regulator, start the car and just fell it, it will fell exactly like how it sounds. sounds weird, but true. also another thing to (happened to me), the muffler could be rusting out, and its cracked, and the more pressure from exhaust goin throu the louder it is. i had a hole about 6inches long and 4 inches across just from exhaust pressure, so it is possible.