I have a 2018 with a Yosh slip on currently on it, but I'm thinking about going to a full exhaust system. Should I stick with the Yosh system or is there something out there that is drastically better? If I stick with the Yosh can I just buy the header and midpipe? or will I have to buy a whole new system?
Why? The bike will make marginally more power, once tuned. It’s a lot of money, for so little. You lose the catalytic converter, so it’ll be smelly. It’ll be louder. It won’t make you faster. And, the slip-on setup you have looks good and sounds good, already. Put your money toward something worthwhile.
If it's a race bike the only benefit to putting on a full system is to get a nice tune installed and dropping a bit of weight. The CBR has really tricky on/off throttle from the factory (at least my 2014 did) and a tune after installing a full system made the on/off throttle characteristics while getting on throttle in a corner much better. But like Ducnut said, if this bike is going to be on the street, why?