Have a 2000 deville that started surging and will not get past 30 mph. Any ideas on 2000 Cadillac DeVille

Car. Has 225000 miles on it. Has not done this before. I changed the fuel filter and that improved performance a little.

2 answers
Sounds like you may have a fuel pump issue. What is the fuel pressure at the fuel rail? I would recommend you have a local shop diagnose the problem.
poss plugged exhaust system also.have a muffler shop ck complete exh system