There's literally no chance in hell a 241/241 with 106 LSA is going to have the same vacuum at idle as a 231/231 with a 110 LSA.. He'd be looking at a loss of 3" vacuum at idle MINIMUM. You need to stop.
OP, I don't know what's going on with your torque curve, but it shouldn't dip like that between 3500 and 4500 RPM. the peak should be right where the dip is.. and a higher figure. I firmly believe 480lb/ft should be within reach!
IMO It should look more like the attached file.
NOTE: the light blue curve is a proposed spark curve with a multiplication factor of 10, So if it reads 350 @ 5400RPM it means 35 degrees advance @ 5400RPM. This is just a guideline, or an example of an optimised ignition advance curve for an imaginary engine of similar specification to yours, SO DO NOT REPLICATE THIS CURVE EXACTLY. but if your spark curve is deviating from this by a large amount (say 20%) in the mid range where you have your dip, it may indicate that your ignition/spark curve needs some tuning attention to remove the dip.
The low end of this spark curve, under 1800RPM should also probably be disregarded, too. Since this is an example of a full throttle pull at maximum load. (an unrealistic scenario for an engine speed that low in your application)
View attachment 1714995679
