99 Buick Park Avenue Ultra cut off after 15 minutes of something one cut on to the later the nation later on that day or the next day

I got a 1999 Buick Park Avenue Ultra and it only runs like 15
minutes or 20 minutes and then it cut off but I just had cut
my Cadillac converters out and added straight pipes and I
cut the governor off change the spark plugs wires coil
packs and it was running everything was working good but
I haven't drove it like probably a month or two and now it
just run for 15 minutes of some and cut off and it won't cut
back on until like later that day or the next day