Accelerating at freeway speeds

[chevychic]

Now that I've been driving my truck 70 miles 2 days a week on the freeway, I'm finding other problems.

If I'm cruisin along at 65 and try to accelerate to pass someone, I start hearing a noise kind of like an exhaust leak (I think) accompanied with a metal ticking noise (like a fan). It's coming from the engine area and I'm not positive, but I THINK it's coming from the passenger side. Kind of hard to tell with all the freeway noise and rattles my truck has. The metal ticking and the air noise may be 2 seperate things but they both happen at the same time. That's the best I can describe the noise so if you need more details just ask and I'll do the best I can.
Once I back off the accelerator, the noise stops and I can cruise along comfortably. It's just on acceleration that I'm getting the noise.
I played around today and found that I don't always have to be at freeway speeds for this to happen. Once my 700r4 shifts into 4th gear and I try to accelerate I hear the noise(s).
As far as performance goes, it seems to bog down a bit when this happens. Not incredibly, because I can still increase my speed but enough for me to know that I'm missing quite a bit of power that could be there.

Just a couple of notes to help you guys out...
I did have a different metal ticking noise that ended up being a couple of loose bolts from my flexplate to tc. Tightened those up and that noise is now gone. (Although I do need to shim my starter now)

Any ideas?