If I'm na and going e85 would switching from a 2.5" exhaust to 3" make a noticeable
 

Would switching from 2.5" to 3" na motor on e85 result in a whp gain and if so is it worth chaining my exhaust to 3" approximately how much whp am I looking at I would be changing my invida n1 catback resonated front pipe and motiv overpipe for ultimate racing 3" full exhaust

Not much. You'll lose some down low and gain a bit up higher. I've already tried it and got rid of it within a few months. Sounded like shit and felt boggy real low 1-2k rpm before it felt normal again. Difference is not worth the rasp you'll introduce with it. Save 3" for turbo.

Thanks for the advice brotha saved me a headache yeah then I'll prob just stick with my setup now I just need to decide on coilovers! Lol

Im na with a perrin 3inch and e85 and it deff doesnt bog down low. (at least for me but everyones car is different). With out getting your tune dialed in specifically for setup then yeah your not going to see many benefits.

if your not planning on going FI in the future then you should be fine with just a 2.5. The gains of a 3 vs a 2.5 inch are there but very minimal and depend mostly on your tune and supporting breathing mods.

2.5in = Anything less than 400whp
3in = Anything above 400whp