Jdm engine rev problem

[Wicked19]

Sorry...

While I am idling in "Park" their is a noticeable miss fire in the engine. When i begin to accelerate in "Park" the engine seems to be a little rough upto about 1500rpm, after 1500rpm i can continue to accelerate the engine and it will smoothly redline. I had to adjust the throttle linkage to idle smoothly.....(i thought the ECU automatically adjusted the idle speed). Whenever i put the car in "drive" and drove, it would not noticeably accelerate, the car had a max rpm of 1500. Im not really sure what this could be, ive compared this car to my other Supra when i install parts and everything seems to be good. This car did sit outside for 4 years and the engine had 275,XXX miles on it before i bought it and installed the N/A JDM Engine. Ive cleared the exhaust and have never swapped ECU's.

Thanks for everyones help!