The car has 47,000 miles on it. 3.8 liter engine. It has allways run great till 2 weeks ago. I change oil religiously, and change air and fuel filter when needed. The problem is this, it runs good at idle and up to 3500 rpm then at 3500 to 4000 rpm it stalls and wont go any more. starts to slow down, looses all power but is still running. when I try to push accelerator to floor it starts to misfire and engine light comes on with a code of misfire. I here something like a click under the hood like the computer shutting something down causing it to do what it is doing. then when you let off the accelerator you can here the click again and the motor starts running fine again. until you get up to 3500 rpm again. right at where it wants to change gears driving normal. I cant figure out what is going on. I changed the fuel filter just to rule that out. fuel pressure shows 59 psi when key is turned on pump pressuring system. when pump cuts off pressure shows 50 psi. when I start car and it is idling it still shows 50 psi. when i hit the throttle it will go up to 59 psi then start to go down. what i mean by hitting the throttle is pushing throttle down a little then letting off. I changed the fuel pressure regulator just to make sure that wasnt it at $50.00 and some change. because the pressure did not drop 3 to 10 psi from pressure at key on fuel pump off wich was 50 psi. actually it should have been 53 to 59 psi key on pump off but it does go to 59 when you first turn key on and pump is pressuring system. and again after it is started and giving it throttle it will go to 59 psi so I am sure fuel pump is okay. problem is the same, does anyone have an idea as to what it can be? I need help, cant figure this out. If it were plugs or injectors it would run bad at idle on up to 3500 but it runs fine to there then wont go any higher. any help would be appreciated.