There are to many variables to say it will hold x,y or z.
But,,,A well respected tuner tunes these to around 250. A lot has to do with how it’s tuned, how it’s built and how well it’s all matched together. Make sure there is NO detination, keep inlet temps down, don’t go for a stupid big or prehistoric turbo, don’t hold it constantly on the limiter and you will be fine. You can use a decompression plate but I prefer the idea of instant response.