A bug in GTA 5 next-gen is causing vehicles with turbo tuning to go slower than those unmodified.
A number of players have reported the problem, which only seems to affect GTA 5 on PS4 and Xbox One.
Some cars and bikes fitted with turbo tuning at Los Santos Customs end up accelerating slower than those without.
Rockstar has said it's aware of the bug, and is looking into resolving the problem.
"We have received reports about issues with Turbo Tuning upgrades in GTA Online and are currently looking into a fix.
If you prefer to remove turbo from your vehicle until this issue is fixed, you can do so at any Los Santos Customs in-game or on the iFruit app," said Rockstar Support.