Hi team. I have done a lot of research about Webers and 13B's and I must say I am more than just a little confused. I wonder if anyone could assist. I apologize for being an utter newb (and yes, I did a search for answers).

Problem:
The car started running rough around the time a new exhaust was installed.
The engine blogs under low rpm and has no power. Runs rough when cruising and light acceleration.
When stationary, it will backfire after you give it a few quick taps of the throttle (less than 3000rpm)
It will not start with partial throttle, but it will start easily without any throttle.

Engine: 13B street port (8.6:1 turbo engine). 200 miles since rebuild.
Exhaust: 2 1/2" free flowing
Lambda at idle and up to 3000rpm: 0.75 - 0.80
Lambda over 3000rpm: 0.95 - 1 (under light throttle)
48 IDA Weber (this is new; 200 miles):
Main Jet: 180
Air Jet: 155
Emulsion Tube: F11
Chokes: 42
Idle Jet: 70F10
Idle Jet Holder: 120
Needle Valve: 300
Mixture screws: 1 1/4 turns out
Fuel Pressure: 4 psi

To me, it appears to be rich at idle and under 3000rpm and lean over 3000rpm. I'm confused if I should go smaller or bigger idle jets or just wind the mixture screws almost all the way in. All suggestions are greatly appricated.

 

70 idle jet is kind of small, most of us are running a bigger one, also the idle mixture screws ideally would be ~1/2 turn out, so that is pointing to 70 being big.

the F11 E tube is for a small air cooled engine, so on a rotary its kind of slow and lean, you can jet the rest of the carb around it but the 13B should have an F7.

if you search, use my name, and this section, i posted a white paper on carb tuning that is really good, basically there is a process, and you follow it, and its easy