I smell gas in my 99 Buick Lesabre while im driving

sometime exhaust fumes get pulled in the cabin from a short tailpipe or leaking muffler, smells the same, the charcoal canister can get loaded with vapors and smell under the hood, then again fuel can be pouring from a high pressure line but that would cut mileage way down and be obvious, let it run in a spot awhile and back up and look for fuel on the ground

First you need to isolate the problem. When are you smelling the gas? 1.)does it get stronger when going down the road actually moving? 2.) is the smell coming from the front or rear of the car? 3.) can you smell it after the car sits overnight? 4.) your overflow vent is probably clogged up. Maybe a mud Duaber or insect made a nest in the end of the line. Use compressed air to blow it out. 5.) look up a schematic diagram for your make model, & year of car. There easy to find on the web . 6) look at it then look up under your car at the gas lines, look for a wet area on the lines or around the fuel pump. Look around the fuel Rails in the engine you should be able to smell your way to the source.

Based on what I read on this site you need to buy a fuel pressure regulator