Have you replaced the supressor boots that connect to the plugs.

A misfire is usually a bad connection between the coil wire and the boot.

Are the NGK plugs resistor or non-resistor?

Your resistance is in the boots, and regular resistor plugs give waaaay too much resistance.

Your problem might not be a clogged hot inlet pipe.

Because you have a bad idle when the car is cold, it sounds like your egr valve is either sticking or stuck in the open position.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".