First of all if this post is at wrong place, please move it!

I downgraded my iPod Touch 4G from 4.3.3 to 4.2.1 because I experienced speed and battery issues, but next I thought about 'Safari' which was claimed to be 2X faster in 4.3.3 than 4.2.1.
Is it possible that I copy a 4.3.3 'Safari.app' to 4.2.1. Will it work? Could anyone post a link to their 4.3.3 'Safari.app'. Plz.