Error code 58 on my Kawasaki Vulcan 1700 e9f 2009

Wot is error code 58 and how to fix it, my bike has been running great for around 17000 mils but now when I start it it runs fine but won’t rev it’s like limp mode,my bike has aftermarket exhaust system and the clean air system off and by passed and a small breather filter fitted, o2 sensor removed and by passed, it also has a Large K&N filter fitted, any help please