Some to-do thoughts:
1 - Check in with your boss on your current status. Typically, 6 months after a PIP, an employee gets a checkin reflecting the status of the PIP and their relative success/failure. Sounds like you have a big success. So it should be OK to say "hey, just checking in here... am I doing well?" You might even want to push for an official mid-year review where your better status gets recorded.
Reasons:
- it's good to know where you stand in your current job
- if asked for an official referral, the company may respond with your current status, and it would be good to have a good status
2 - Check in with HR on the company's employment reference process. At least in the US, this is a public policy that all employees should have access to. And there's all sorts of reasons to ask about it, because it should also apply to you as a person giving a reference for someone else, so it's not just a "hey, I am looking for a new job..." sort of thing.
Then you'll know, for sure, what the company says about you. Often you can even get the hotline and make the inquiry yourself, to verify your state.
3 - Paint a success story. It is not "I did my job so badly I got put on a PIP, then I recovered and now I'm great". It's "I got some great management feedback about X, and that led to me figuring out some better ways of working. From that process I learned Y, and it's make a big impact on my productivity. I'm now among the best in my team, and I deliver Z value to the group I work with."
- X = whatever the PIP was about
- Y = what you changed
- Z = in business terms, what being a top rated performer means.