There's a good chance that you would be able to run it that way safely for a while. Also you wouldn't have to have a dyno tune. You could get a remote tune and although it isn't any cheaper than a dyno tune it may be better for you since you are just looking to do one piece at a time since you get free retunes with those.I know the lambda sensors are useless for afr. I want the cats just dont wanna melt a piston doin it. Wife already thinks its unpractical so gotta do alittle at a time so if I got the cats I dont know how long it would be between cats and dyno tune lol I heard the commanded afr by superchips on the 91 tune is 12.6ish and stock is pig rich so if I log this and feel its lean I guess id just use the stock tune till it sees a wideband ?