[Turbo Den]

hello,
i've tried searching the forum on cold winter carb adjustments, but no good result. so here's the story and question.

this is my 1st yr with a P-car, and 1st yr with carb.
it's 1978 3.0 SC w/ PMO carbs. run very well in Vancouver summer 15-25 degrees C' / 59-77 Fahrenheit.

my brother came visit last week, so i insured the 911 to show him how good a 30yrs old porsche is still a porsche. but i failed to impressive him totally. cos, the car wasn't running properly.

warmed idle is 800-900 rpm, normally 1200 rpm.
engine CANNOT rev past 3-4k rpm, normally rev happy to 6500 rpm.

question: what would you do, if any, to adjust the carbs for cold weather?

i tried full gas tank, long warm up, 1-screw counterclock wise on each mixture adjustment screw for more fuel.

thank you.