Looking for input on M42 exhaust.

[Jaredmac11]

I am running an M42 in my e21..  Setting up exhaust from scratch.  Im in TX and dont need a cat, but I was thinking cat, resonator, muffler exhaust system.  With either E30 stock 2.25" or upgrade to 2.5".  I know a lot of folks go up to 2.5"  but I was wondering about what I would be losing from losing that back pressure?  Is the mid-range softened up or do the RPMs fall pretty quickly?

I feel like a lot of folks go from a 20+ year old stock exhaust system to a new 2.5" so of course its improved but Im wondering about folks who may have tried multiple setups and can compare apples to apples?


THANKS!