Thinking bout putting my stock muffler back in, do I need to change my customs tunes for that???

 

If its just a muffler swap....then no you dont

 

nope

 

Do tires make a difference, had 285/65 18's and now have 305/65 18's , new to the tuner world so apologize if some of these questions sound crazy, and thx for the replies

 

You can and must adjust for the size difference using the end-user settings on the handheld, before the flash process begins.

Please read the stickies at the top of this forum, AND the User Guide for yer programmer , AND the website Help and FAQ sections for yer specific device - everything you need to know is going to be explained there in detail.