What exhaust, if you don't mind my asking?
Anyhow, an overview of the Florida points system:
Florida Traffic Violation Point System
Quickly looking over § 316.293 (
link), if it's louder than stock, it's illegal and you can get ticketed & pointed accordingly.
Assuming they're sold locally in the state, contact the manufacturer (or the local distributor for them, if needed) and ask them to send you a copy of the certificate that they filed with the Florida Department of Environmental Protection stating that it complies with § 316.293 (which they're legally obligated to do under § 403.415). Or even, just try and find the manufacturer sound measurements for both the stock exhaust and also whatever one you had installed.
I'd think that, and I'm not an attorney so I have no idea whether or not it's a valid defense, but if it was bought and installed in-state, you'd be able to contend you had a good faith reason to believe it legal (otherwise it couldn't be sold within the state).
Overtaker: the statute doesn't say that the Officer has to measure it with a dB meter in order to write the violation. It's merely directing the DEP to help loan meters to law enforcement. Key difference; you won't get out of it by just saying "hey, no dB meter!" Rather, you need to prove that the exhaust is NOT louder than stock.
Simple as that; even if it's just a hair louder, it's in violation. The exact measurement doesn't matter.
Of course, if Ranger were say accelerating or had missed a shift (or was sitting in too low a gear, even), that would certainly make it a louder note.