Check engine light

Hello all, just purchased my first Ferrari! 1994 348 spider. The car was neglected for a few years and is three years since the last belt change. It was purchased by an elderly gentleman who drove it for a few hundred miles and then parked it in his garage rarely ever even starting it. I purchased it as a running project and I’m trying to work out the bugs. When I got it, it started but smoked a lot and smelled like bad gas. I drained the fuel and filled it up and added some seafoam. It’s still smoked and ran poorly. After some thought I decided that I would change the spark plugs as they were probably fouled from the bad gas. After putting spark plugs in, it ran slightly better but still not like it should. It was throwing The check engine one through four light. I also noticed that it had a hard time staying running When it was hot. After a little bit more research, I decided to change the O2 sensors as they were probably fouled by the bad gas as well. After switching both out, again, it ran slightly better but not as good as it should, still smoked and still had a hard hot start. I decided to change the oil. Following manuals instructions I discovered that the Oil smell like bad gas and the level was higher than it should’ve been when hot. I put the proper amount in and still got the check engine light and it did not run as good as it should. Looking at the fuel pressure regulator’s, it look like Somebody had replaced the driver side but not the passenger side. I pulled the vacuum line out of the FPR and it had a lot of gas in it. I bought 2 FPRs and replace both of them. Now the car runs great! Doesn’t smoke at all and hot starts as well as it cold starts. After about 5 miles of test driving however, the “check engine 1/4” light came on again. Any suggestions?

 

Thanks! So far it’s been a fun car to work on. Everything is soooo easy to get to. All of the systems are very simple and well designed. I’m impressed.
Took the car out again. Light was off for the first 3 or 4 miles then came on for a minute, then off, then back on then off again. Meanwhile, it sounded perfect and what a power curve! Besides the light it’s running perfect.
Reset the ECU and will try again tomorrow