Originally Posted by flight01
How was the m7 faster? In what way?
Yeah, I agree that the OP hasn't given much detail or specifics. Only thing I can think is that AT&T bloat is slowing his device down. Which you mention, and is not unheard of since the AT&T bloat is often ridden with bugs and poorly optimized.
Other than that, the M8 is already blazing fast, smooth, and a joy to use. OP can explore custom ROMs that have various optimizations; and/or try custom kernels which would enable overclocking. But its not clear what is trying to be accomplished. Slow just within the OS interface, certain apps, or gaming?