Diesel Bombers - New Turbo.......Less Power??

Hello everyone, needing some help on my 04 2500. It has 155000 miles on it now. When i bought the pickup The edge juiced with attitude was already on the pickup, as far as what else was done to it before i got it i have no idea. im thinking it had bigger injectors also since i can turn the edge tuner to stock setting and still role the coal. Since I've bought it, the transmission was totally gone through and beefed up. cold air intake, head gaskets and studs, and i installed 5in exhaust off the factory down pipe all the way out the back. ok heres the start of two weeks ago when i noticed issues. on the way home, it started acting doggy, i look in the mirror, even trying to run 60 down the highway there was black smoke coming out the pipes and i could only build 5lbs of boost. even trying to powerstand, 5lbs of boost. air to air and tubing was fine and no leaks, so i deemed the turbo was bad since it was blowing smoke, but wouldnt spool up. I purchased a BD supermax turbo kit, Bd exhaust manifold for the drivers side, and got the larger down pipe. got everything installed, and i swear that the stock turbo ran better on the pickup. if i put it on a high idle at 1500, it'll push roughly 2.5psi of boost, slightly longer turbo lag from what i can tell, but once it spools, its right up around 26 to 28 psi.the turbo i bought said it was good for 550 rwhp, and could be ran around 45psi, i havent touched the wastegate adjustment yet. Even one wet pavment, i cant break the tires free, it doesnt smoke anymore, except when its at an idle and i can on it, ill get some smoke like before. but after that i have nothing it seems. it sad but im sure my brothers 6.0 would probably run circles around me!:scare2: i need help. Where do i check first? Are there any sensors that could be affecting? if i would have went back with a stock turbo would i have still had problems? i have no idea where to start. I work on semis all day long, but i dont have a very good clue what components are on my LB7, or where to even start troublshooting. my first guess was to go to the fuel system. change fuel filter for a cheap start. didnt help at all. where do i check fuel pressure at, and what should it be?