Slowly, I am restoring my volvo 240 1990 dl. It has a 165k miles on it(at least i hope so, but i am worried it may of been a frankstien car put together at the volvo dealership/shop). I want to improve my idleing. It's is pretty smooth for the most part. But every once in awhile it will idle rough or be a little rough deaccelerateing. This isn't constant, but just once in awhile. Also, when I start my engine while it's hot from running previousely, the check engine light will come on for a sec and it will want to die out untill i give it gass. but this is only when the engine is hot.

here's what I did so far:
new fuel filter
New oxygen sensor
Tune up with new rotor cap and wires
new flame trap filter
new starter
new fuel pump

What should I replace first?
1)The fuel regulator
2)The idle motor
3)Air mass meter
4)Fuel injectors
5)in tank fuel pump

 

I would clean the idle motor and the throttle body. Also check the accordion hose for leaks.