O2 Dump tube

My friend blew his tranny and is selling all his parts, and he wants to sell me his dump tube...I was wondering, if I have the stock exhaust manifold on the engine now, if an O2 dump is going to make a big difference? If it will then I will buy it...but I don't know if it's one of those things where it won't make a difference unless you have other things...like an aftermarket exhaust manifold...
let me know.

Do you mean o2 housing with an external dump or an external wastegate setup that dumps to the atmosphere? If it's just an o2 housing with an external dump then do not buy it. It will help nothing. If it's an external wastegate setup, then I would buy it (considering its a decent price) if I planned on going to a large turbo in the future.

He just calls it an "02 dump".....but it's just connected to the "left" or drivers' side of the exhaust manifold....just bolted on..I know what the wastegate is but I don't remember if it's attached to that or not...

He says it will get rid of my "boost creep"...which I am assuming is the same thing as turbo lag?

You aren't clear on what he is selling. On externally wastegated turbos, there is a tube that bolts to the wastegate to direct exhaust gas away from the engine. This is of no use to you on an internal gate. The only way to dump out of an internal wastegate is with a dumped o2 housing... not recommended.