Fluttery Noise from Engine compartment on cold start

[Rendell]

I have a 97 4wd Limited, V6 3.4L. 228K miles. New A/C front to the firewall last year, and timing belt 3 years & 10K miles ago. It's my Daily driver. Yes, I leve about 2 miles from work.and drive my wife's car when we go somewhere. I had the valve cover gaskets replaced, at Toyota dealership, about 2 weeks ago. It had the standard 3.4L valve cover gasket seeping. It also, had the standard lift gate latch cable breakage fixed at the same time, and the brakes bled (I did the tundra brake upgrade, and had to do the bleeding solo.. So, I had the breeding done while it was in the shop). Anyway, The truck went in for the valve cover gaskets, and never had any strange engine compartment noises, since I've owned it for 3 years. After I got it back and it was cold (For Arkansas, 40F) this morning, I started the truck without getting into it, as I had to start it then take out the trash while it warmed up a little. For the first 10 to 15 seconds there was a fluttering noise in the engine compartment. then it went away.. It sounded to me like a exhaust leak at the manifolds.. I'll be calling the Dealership that did the repairs, because I am not accustomed to spending $950, to get my truck back with new problems.
My question is has anyone had a similar issue with the truck, not the dealership, as I expect they will make it right. It sounds like an exhaust leak, then it runs for 10 - 15 seconds and warms enough to seal.. Does it sound like I'm way off on that?
Thanks in advance.

 

[DARINnVA]

Sounds like an exhaust leak. Could be just a gasket blown out of could be a cracked manifold.

 

[Be_Original]

At that mileage have you ever had your valve clearances checked. Loose rocker arms can get quiet after warm up since the tolerances change. Just an idea.