Engine idles rough.
 

I have a 95 Blazer 4X4 with the 4.3L V-6. The motor has excellent throttle response off idle, runs well, and produces alot of power, I also get 15 MPG. My spark plugs are new and of normal color. Cap, rotor, and wires are also new. I replaced the fuel injector assembly and fuel pump 2 years ago. At the tail pipe I get an uneven lope with an occasional puff sound. Is this a vacuum leak problem or exhaust leak?

best thing to do is record it , throw it on youtube and post the vid here... better to help ya