I am trying so hard to get my 3.5l 1999 Diamante to run correctly and I have replaced a lot of stuff. First off let me explain what it does starts perfect and idles perfect until I press the accelerator then it hesitates or stalls. But if I press it halfway or more it revs decently. Sometimes it will stall at red-light sometimes it won't. Engine light goes off and on when on it codes a random misfire. I have replaced the fuel pump, fuel line, distributor cap, rotor, wires, plugs, vacuum lines, and cleaned maf, tops, and fuel injectors. I have no other transportation and really need it for work 😩. Any ideas or ways to troubleshoot would be great. I'm not able to get a bunch of new parts unless I know they will help. I love my old friend but ready to give up. Mechanics want a arm and leg to start troubleshooting it. Thanks for any help or advice!

 

Have you adjusted the TPS correctly?
MAF is the next most likely. When they fail anything can happen.