99' E430 issues
 

Help! My mother called me and her 99 e430 won't accelerate over 60 mph. She also tells me that her check engine light comes on when her fuel gets low or when she get's fuel from time to time. We were thinking it was a bad gas cap and replaced it.

Would a bad fuel filter be at the root of these problems?

Need to get the codes read and go from there, my guess would be the MAF sensor, could be lots of things though so don't go replacing anything until you at least know what the codes are.

Would help to know the mileage on the car in reference to the fuel filter, could have a tank of bad gasoline I suppose too, seen that before.
These things need to be maintained, if it is high mileage with an original fuel filter, well yeah you should do it, you don't do maintenance based on some problem, you do maintenance when it needs to be done, so find out what should be done and when and if it is passed due then make sure it gets done, air filter, fuel filter, spark plugs, cabin filters, keep up on maintenance!