My 91 Cadillac Started Hessitating For The First Time Today On The Interstate

it kept losing speed I could barely get it to maintain 45 let alone get back up to 65 the speed on the interstate. I tried shifting it into 3rd that didnt work. Finally made it to an exit and barely got it to a parking. I checked all the fuses (under dash & under hood) I switched out the fuel relay with the trunk relay, none of the fuses are bad, but cant see through a relay.I also loosened up the gas cap, I recently replaced it due to the charcoal filter in it was bad (most likely due to age), when I loosened it I noticed a lean gas smell, but I was at a gas station.  I got on the highway instead of interstate this time. It was running alot better but just in case, I stopped at got more gas and then tightened the cap to see if there was a difference so I could diagnose problem or elimate a cause.  Leaving there on the highway it did fine for 25-30 miles and got up to 60 on highway fine, then did it again. I pulled over again and thought to loosen up the cap, because it had ran a little better with it lose after I pulled over the first time, when I did this time there was a strong odor of richly burnt fuel, luckily I was a mile from home & it continued to hesitate those 2 miles. When I say hesitate it's acting like it's starving for fuel and the hole car is jumping (physically not in timing or elctronicly). I say it smells like burnt rich fuel but with so much Ethonal in gas now a days it smells different than the smell that used to come from my old Monte Carlo when the carb needed adjusting, so it may be lean. I am thinking fuel filter or injectors. I also left my manual at a friends I would like to know the location of the fuel filter and a second opinion based on the above info & common issues with this car. Thanks in advance.