Since no one else is helping (communities man), I suppose I can. First load the cod4 alpha and find a function to your liking. Once you have, open a new instance of IDA and load the mw2 default_mp. Go to the cod4 and copy some of the ppc code that is uncommon (such as "lwz r9, 0(r5)"), then go to hex view and copy 4 bytes for every instruction that you are copying (each line of code takes up 4 bytes in mem). For example: if you were to copy "nop" the byte equivalent would be 0x60000000 or 60 00 00 00. Once you have the bytes copied, go to the mw2 ida window, hit alt + b, and paste the hex values. If you find any hits, compare code and determine if any is the function you're looking for.
Note: this is NOT the best way to do this, its actually quite horrid. This is for beginners, or people who don't know how to navigate ida.