Check valve clearance and timing first. As stated above dual DCOE Weber's definitely like a good amount of initial advance, my engine likes around 15 degrees. A good working air flow meter is an absolute must. Float level is also critical to a smooth running setup, check for potential faulty floats, plastic ones are a little harder to catch than the brass ones. On that note there are notable differences between new and old style (Italian and Spanish) versions of the DCOE. Most important of these in tuning is the thread pitch on the air/fuel adjustment screws which are approx. 50% finer on newer versions, so 1:2 ratio if you are working off all guidelines. Another difference is the newer DCOEs have more progression holes for better low speed drivability. As I've mentioned elsewhere, working off old charts is a great starting point but I suggest an increase of roughly 10 percent in fueling requirements as modern fuel is watered down a bit from the days of old.
I've experimented with 36, 34 and 32mm chokes in my 45 DCOEs. I've found with a mild cam and mild compression 34mm chokes seem to work well with a strong pull to 6000 RPM but every engine produces a unique vacuum signal. 32mm chokes work as well in 45 DCOEs but start to sacrifice top end RPM and are technically out of range of a 45 DCOE and should be much more efficient in a 40 DCOE because you are creating less of a wall for the air to pass through at higher air speed (32mm choke in a 45 DCOE is thicker overall than a 32mm in a 40 DCOE).
Correct Idle jets are usually the most critical for a well behaving engine as they control how the car feels for most around down driving and that will usually require some experimenting, I've played with both idle jets in the F8 an F9 families (different air orifice sizes) in both 50,55 and 60 sizes to find what my engine likes best. Emulsion tubes are a whole topic unto themselves, it's best to stick with what is known as good working tube, F16 are the most common but others work as well. Generally speaking you'll be working in the 130-140 range of main jets and 180-200 range of air jets, generally a gap of 40-50 between the two works best. Keep in mind you are on the idle circuit up until around 3000 RPM before it transitions into the main circuit. Sometimes I find due to gearing, wheel size, etc. that we are sitting right at the transitional RPM at cruise speed on the freeway and that can be at best annoying, at worst frustrating and there can be a lot of time spent just tuning for this scenario which is second only to idle characteristics.
At the end of the day it takes a bit of fussing around to get these about 75% right and a lifetime to get them 95% right. Changes in weather/temperature/seasons also effect these carbs as well as wild swings in elevation. I've been fussing with mine for about 8 years now on a fairly consistent basis as I'm always trying new things but once you get them close then you are usually good for quite some time.
A side note, quality control between Spanish and Italian Weber's is quite apparent from anyone you talk to that has been fiddling with these for any amount of time. I've had lots of odd malfunctions over the years with my newer Spanish DCOE's that has me ever loosing confidence in them (like cold start valves that would jam open with even the smallest carb backfire because of poor manufacturing tolerances and cause them to run lean constantly). On the flip side finding a good set of Italian versions is getting harder and much more expensive every year.
PS. Please for the love of everything that is scared, do not fiddle with drilling or modifying anything. Jets are readily available and require a minimal investment, if you can't afford jets you shouldn't be stepping into a set of DCOEs. They even make tidy jet packs for a reasonable price that come with a variety of sizes.
