Hello, my name is Jason and I recently purchased a 2003 grand marquis. I've only owned it for a week but this is what I've learned so far about the car. When it rains a lot there will be a puddle of water that pools in the rear passenger floor. From what I've learned on you tube this is common in all panther cars. Supposedly it's an air cabin filter I need to replace. I have one on the way if anyone can confirm my purchase to stop this issue. The main reason I bought this car is because the frame is in great condition and the motor purrs like a kitten, and the transmission shifts so clean. There is 312000 on the odometer. This led me to believe this car has been cared for and loved and had things replaced as needed, and that both have probably already been replaced. I am putting on dual exhausts and deleting the last 2 cats, using an H pipe, 2 flow fx mufflers. I also have the 70mm upgrade throttle body from the vans on its way. From what I understand it's essentially a plug and play type deal with no tuning needed. Someone please correct me on anything you see where I'm wrong in my research. For now I plan on using the stock air box and hose. I've learned that to get even more air flow you should change the air box and hose to the PI box and hose. If I change the box and hose I see on you tube where a guy had to change his mass air flow sensor. I'm looking for comments about this. While just changing out the throttle body no change in mass air flow sensor is needed. Thanks any tips or tricks are greatly appreciated.