A 40 with 34mm chokes should work OK. I have vague memories of setting a 40 up on both of your manifolds on a motorkhana special over 20 years ago. I remember staying with the two pulse manifold as the owner liked it better. I do think twin 40s with 30mm chokes would be the best solution, and may clean up the idle and low down somewhat as well.
The A6 Cosworth is a very large duration camshaft that is just not going to make a lot of torque down low. In a hot street type engine I would be looking at less duration so the engine is nicer for the 90% of the time you are under 4500 rpm. An A3 Cosworth would drop 30 degrees out of the duration at 50 thou and wouldn't be throwing so much fuelled up air out the exhaust at low revs. I used an A3 Cosworth in a 16TS engine many years ago with twin Webers, and was very happy with the idle at 1100 rpm and the power delivery. It came in quite hard at 3500, but was nice enough below this.
Road cars are always a compromise.
The A6 Cosworth is a very large duration camshaft that is just not going to make a lot of torque down low. In a hot street type engine I would be looking at less duration so the engine is nicer for the 90% of the time you are under 4500 rpm. An A3 Cosworth would drop 30 degrees out of the duration at 50 thou and wouldn't be throwing so much fuelled up air out the exhaust at low revs. I used an A3 Cosworth in a 16TS engine many years ago with twin Webers, and was very happy with the idle at 1100 rpm and the power delivery. It came in quite hard at 3500, but was nice enough below this.
Road cars are always a compromise.
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