Dead end in a problem w/ my b12

[tmfollick]

Hello everyone,

 

I bought a b12 sentra that had a nasty rattle coming from the engine which ended up being a spent timing chain guide. I replaced all of its timing chain components and front engine cover, While I was at that task I decided to change all the spark plugs, spark wires and cap/rotor. I got maybe 12 thousand miles out of the car and then I started having a throttle issue...The problem I am having started when I was driving on the I-5 commuting home. I noticed a flat spot in the throttle, I could cruise along fine at any speed at about 1/4 throttle, then half would start bogging down and as soon as I hit 3/4 it went away. My first assumption was the throttle position sensor, so I went ahead and replaced it. I plugged the new one in and it was reading right where it should be .5v at idle and somewhere around 5v at full throttle. I hopped in the car to take it for a spin and I still was having the issue, so I did a little more digging. My next move was to check the fuel system so I ran a pressure gague on it. My manual says it should be around 35psi and I'm getting a bout 65-70psi. Once I saw that pressure pushing out I figured it was the fuel pressure regulator so I raplaced that and now my car is running worse. I did a bit more poking around and realized there is hardly any fuel coming out of the throttle body into the return line and there wasn't any vacuum to the line above the butterfly valve in the throttle body, I split a vacuum line to put a T-valve in and steal vacuum for the line in the throttle body and i'm still having the same issue with hardly any fuel coming through the return line. Does anyone have any suggestions what could be causing this?