heh, well thank you!
The ideal number to shoot for when it comes to Speed on Agiligross is 198 at level 100. That would guarantee that after a single Agility, Metagross will outrun everything with base 130 Speed, beneficial nature, and maxed EVs (such as Jolly Aerodactyl). Anything beyond base 130 is not really of interest. With perfect IVs, Metagross needs about 88 or so EVs minimum (I think Samson told me once). Generally 106 is a good EV number to shoot for, but with a 21 IV in Speed, it's definitely worth the extra EV investment just to make sure. I'd suggest taking it into WiFi battles to see when it reaches around 198 (you can start with 106 EVs in Speed, check, and then add more after that if needed, since after it reaches 198, the extra EVs would be useless). Once you do get an ideal number (198 is the bare minimum, I must stress), then the extra EVs should go into HP or Defense. Preferably HP, but I know people who choose to put extra EVs into Defense.