I just bought a new slim. I haven't even opened the box yet. At the same time I bought a used phat. Unfortunately the phat is running 3.71 official firmware. Is there any way to downgrade or apply m33 to 3.71 official firmware on a phat yet?

doesnt pandoras battery work......i think my phat was on 3.70 or something along them digits....

Hi Chris B, and welcome to Console-Spot.

About downgrading your 'phat' PSP on 3.71, read my replies here.

So it seems the only way is to have a a phat capablel of running 1.5. Darn that's why I bought the used phat. My luck I guess I can return it and try to find one that has and older firmware on it that's capable of being down/up graded. I don't have access to a PSP running 1.5 or any other custom firmware. Now I do have a memory stick from a psp that was running custom firmware it's from my old unit that shorted out. Is that of any use?

The memory stick is of no use.
You need to be able to convert a battery into a Pandora's Battery.