Normal sound? Exhaust Leak? Worse?

[yeehoo]

I don't know what this sound is. If someone does please let me know. Basically, Idle is good no issues, ease into the gas no issues but, when i get on it I hear a thumping sound. 4.3 tbi, 217k . Attached is a video i made its kinda garbled at first the sound I am referring two is towards the end from about 22 sec mark to end.

https://drive.google.com/file/d/0B8gErgcbey9UUm9VWjltSEtGRmc/view?usp=sharing