It's not clear how much time has gone by since this purchase, but if there's mileage and upgrades, it's probably been awhile, and there may also be an issue about whether you could have discovered the actual number of engine cylinders yourself by inspection and whether your reliance was reasonable, no matter what the ad and salesperson said.
In FL, fraud remedies for a material misrepresentation of fact that you reasonably replied on are either rescission (cancellation) the the sale, where you give the car back and get your money back plus the cost of your upgraded seat covers if you can't use them on another car, or affirmance of the sale and your damages for the difference between the car as advertised and the car you got.
If you want to keep the car, maybe you can negotiate with the dealer for some free labor services now or in the future. If you want to return the car, you shou;d get your money back plus the cost of the seat covers if they're custom and not jusable on another car. Your time is unfortunately not compensable, nor can you punish them for their mistaken ad.
Disclaimer: I'm only licensed in CA. Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.