I am doing exhaust on my lu5 305 and I want to go with the reg 2.5 inch dual tubes. I was just curious if going with 3" exhaust throughout would be a waste of money compared to 2.5 which are probably suited for 305 with minor mods.

Read this.

https://www.thirdgen.org/techbb2/sho...t=backpressure

Ed does a great job of explaining all of it for us. (Thank goodness. Maybe now some people will understand and actually listen. )