On my 88 MR2 SC I lost a little low end power when I got rid of my catalytic for a straight pipe, so I put it back on because I mostly do my driving on the local roads. But for high RPM driving on the highway it felt like the motor wanted to rev a lot more freely with the catalytic restriction gone. The way I can best explain it is, when you remove the cat it feels the same as when you first put on a performance exhaust.
2.5 is perfectly sized, my friend has that size HKS Hiper exhaust on his 4AGZE AE86 and I can't believe this exhaust was originally designed for NA application! It really suits the power of the 4AGZE nicely, his car is quick so yours must be insane RavenX!
That's a sweet looking hatchback too!