strange exhaust sound '95 5.7 tbi

[mbb]

When my 95 tbi 5.7 is cold, the exhaust makes a strange sound, like 1 cyl is loud. I dont think I have a leak. I can barely hear it inside truck, but was much louder when I heard my wife drive away one day. It gets a lot less noticeable when engine is warmed up. could this be a valve that needs adjust or bad lifter? I have recently checked compression, its fine. Manifold vaccuum is fine at 19" and rock steady, new wires, dist, rotor, fuel filter. timing on the money at 0 too.

the sound really doesnt occur without a load on the motor, revviing it in Park doesnt do it, it sounds smooth. I have listened around engine, exhaust, esp cyl heads at idle with stethoscope and cant hear anything abnormal then.

I had a problem that I think was a faulty injector too, that went away. after not driving truck for several weeks, it stumbled, bucked, knocked, etc and just didnt want to go under acceleration. this cleared up after some B12 chemtool in gas, and hasnt returned. My idle is slightly rough also, barely noticeable.