I found a really clean 2018 Mustang GT for sale, but the owner says it has an aftermarket tune and some bolt-ons. The price is tempting but I'm terrified of inheriting someone else's headache, especially with how hard these cars get driven here. I asked if he had any dyno sheets or logs from when the work was done, and he just said "trust me it runs perfect." Yeah, no. I want to get the car properly tested before handing over any cash, but most mechanics I know just do a basic compression test and call it a day. Would a place like Dyno Star Workshop be able to put the car on the rollers and actually show me if the air fuel ratios are safe or if there's any knock under load? I figure if the seller refuses to let me do that, it's a huge red flag and I walk away. Has anyone here done a pre-purchase dyno run on a used modified car? How much did it cost and what kind of things did they find? Really don't want to get stuck with a money pit.