1998 se help question

[Freddies98se]

Hi newbie here.
I have a question maybe someone here can help me. Here is my story, question later.
I have a 98 900se convertible that I bought about a year ago, up until about a few weeks ago everything was fine and dandy but here is what happened. I woke up one sunday morning tried to start my car and nothing happened, so after a few attempts it was a no go. I went thru the motions of checking all possible problems until I found out that it was the fuel pump, so after ordering the pump and trying to replace it I broke the check valve which left me stranded for another week until I got a replacement check valve, it turns out that after buying a new check valve and replacing it on the car it worked for a day, then the next morning car would not start, turn out that the valve did not work either, the little valve got stuck an it would not let the fuel go by, so after another ordering of the fuel supply line including the check valve once I got the part I installed it and my car started with no problems. When i put the pump i noticed that my fuel gage only went up to 1/4 of the tank when it was more than 3/4 full. Here is where I am at. My car started throwing codes out that were non existent before, first code P0741 , then P0302 and now I have all these codes including P1416. One of things that I am noticing that according to the SID it is giving me better mileage.
I have changed already the following items on my car:
Direct ignition cassette
Spark plugs
All vacuum lines around engine
Fuel filter

Here is mi question can all of these things be related to me changing the fuel pump or are all of these things in their own separate problems? By the way turbo gauge will not go into the red no matter how hard I step on the gas pedal. The car in itself is not running rough or anything but it is bothering the (bad word) out of me that I am getting these codes so I don't know where to start.
Please if anybody can give me a clue of what is wrong with my car, I would gladly appreciate it, as I right now I cannot afford to take it to a shop.
Thanks in advance

[protech5]

One of the biggest issues is the check valve to the fuel pump but you would be surprised how often people put the wrong valve in the wrong line on the pump. This can cause major issues with errors and functions of the pump on rest. Check that although you may just have an issue with the Oxygen sensor.

The turbo problem with excessive boost I would bet is a vacuum leak.

[Freddies98se]

Here is what I don't get if the check valve is put in the wrong place then the car would not even start, correct? I mean if the are two places to hook up one would be the supply and the other would be the return so technically there would be no fuel supply.
Now I forgot to mention that the front O2 sensor has already been replaced about 4 months ago so do you think that the rear one needs to be changed as well?
Can the pressure regulator be causing any of these problems? I tried looking in here in the parts section but I didn't see one for the 1998 900 SE 4 cylinder turbo, does that mean you don't carry it?
As far as vacuum leak where should I start I have already changed all the vacuum hoses around the engine are there other ones that I would need to check? Would they be connected somehow to the turbo itself?