Depends on the miles, after 10,000 km / 6200 miles the hp's should be down to the original starting level, and going down from there.. so no point before then really.
I don't like to tune race car I like to race with them with spec that they have in real life! Its stupid to drive TT race car with 600+ hp when he have 480 hp in real life...
Theres no way an oil change made a 480 HP car 625 HP, nor would an engine rebuild.
Does it need it? Probably not, change the oil and race, see what happens.
Incidentally I do buy turbo upgrades for some of my race cars that I use online because they are easily removed when I want to run stock, but easily added back on when I'm in a room with people who can't help but dump every credit they have into a car. Its nearly impossible to get a "stock" Super GT or DTM race online.
I don't like to tune race car I like to race with them with spec that they have in real life! Its stupid to drive TT race car with 600+ hp when he have 480 hp in real life...
This is what happens when I surf this site at work. That response was sitting on my computer for like 15 minutes before i sent it, because i had to respond to some emails or something, and in that time you had responded to the question about the turbo.