I’ve owned my 12 valve for about six months and I’ve been redoing it the entire time and I knew it ran and sounded great when it ran but today I decided to give her some beans after sitting for two days and it backfired. Not sure if this is something to be concerned about but I don’t know any engine mods it has when I got it I wasn’t told much about performance parts. But it rolls a little bit, so I think it’s got better injectors.