I bought a iphone 3g from ebay that had a bad lcd on it, and replaced it. After fixing it, it booted with a passcode, and seller sold it for someone else so he didn't know it. So I decided to go into DFU mode and do a fresh restore with 3.0. The problem is, it is really slow and hangs up alot. How can I fix this. Is there a way clear data out of it, besides a restore.

It seems to be more during boot up and shutting down, and installing apps. Apps seem to open regularly once I am at home screen

maybay something broke when you replaced the screen :S
some hardware inside