Newbie needs help lol... my 2000 Celica GT is a cancer!

alright. first, thanks for taking the time to check out this post. brief history of my celica. first my brother bought a 2000 celica gt, from new york, with 145k, for 5g. then once it got here, to louisiana, the starter blew... brought it to the dealership, fixed it, then within 300 miles, engine BLEW! so i bought it from him(bad idea)... anyway. i bought a facelift motor from 2005, with 15k on it. got it all installed, ran pretty good. kinda hesitant, but ran pretty good overall. i just put 3500 miles on it. well, on my way to work, it was running good, but then it got shitty. my gas pedal turned into an anti-gas pedal, lol, it went slower, so i downshifted, pressed the gas, slower it went still. came to a complete stop, engine died,couldnt start it. well, got it cranked up again, press the gas, sucks too much air, bogs and then stalls out. so i checked, fuel pressure, 55psi at injector rail. changed my spectre Air Filter, checked for Intake leaks, vac leaks, cleaned my MAF sensor. no change. so i bought a new MAF sensor, still no change. checked spark plugs, all good. checked coilpacks, all good. so i got fuel, fire and air. no go. now it won't run, i get it cranked for a few seconds, and it dies out. im totally fricking lost, and have no idea what the hell to do. im broke, and dont have a ride. ive been googling and searching all the celicahobby posts, still dont know what the hell to do. i would appreciate ANY help, and i thank you so much for your time reading. IF ANYBODY CAN HELP ME..... I WOULD BE SO GRATEFUL. IM JUST SO LOST ON THIS, AND NO ONE SEEMS TO HAVE ANY INKLING ON WHAT NEXT, SO PLEASE, IF ANYBODY KNOWS ANYTHING... PLEASE HELP. LOL.. THIS IS A PATHETIC SITUATION. THANKS AGAIN FOR TAKING THE TIME TO READ THIS SHITE!