1996 Cadillac sts, 145,000 miles, north star engine
Yes that could be the fuel pressure.
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About your vehicle.
You will want to check the fuel pressure to see if it is too low. Also that the filter is not restricting the flow of fuel.
Then, the exhaust may be a little bit restricted. You can have a back pressure test done on it at most exhaust shops to see if the cat is clogged.
If they are both ok, then you will want to take a sample of the fuel to be sure that it’s not contaminated.