Engine bubbling?

[The Baron]

Hey all! So in my 98 K1500 which has the 5.7L vortec, I've recently noticed a bubbling sound in it when idling. Ever since I bought the truck it has been running rough at idle, to the point it shakes my hula girl on the dash. In park it doesn't shake, but you can hear what sounds like bubbling, almost like a harley or a Carb'd engine. It does bog down a little when i reach around 40 MPH, and then again around 60. It came with a superchip in it. I just had a shop put on new plugs + Wires, cap and rotor. The Motor has around 80K on it. Anyone have any ideas about what could cause this? Also, my exhaust rusted off, so i simply have the original Cat, and nothing more coming of the motor. I know my intake mainfold leaks slightly. But I don't know of anything else that could cause it.

 

[sewlow]

Air in the cooling system? Mine makes a bubbling sound if it hasn't been 'burped' properly. Found that if the front of the truck is raised (up a bit of a hill, or on jackstands) & running, so that the rad cap is the highest point above the engine it helps to let any air get outa there. Sometimes it takes a bit for it all to get out.