I put a new fuel filter on my car now it wont start. on 2000 BMW 528i

It always started before that.so now i put a fuel pump,and pressure regulator on it and still No start. What could it be PLEASE HELP!!!

Asked by for the 2000 BMW 528i
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Why did you replace the filter to start with?
One time months back it was drivivg really slugish.once when i was leaving work it didnt start right away (i had fuel) but it did start 3 minutes later.i put the carMD on it and it kept saying fuel. I already had a fuel filter for so thats what i started with.My machanic put a fuel pressure regulater on it yesterday it still wont start.I know these cars have all types of security features. I shut the fuel pump down on my 325i by putting the key in the trunk. Im thinking thats whats wrong with this car