It may be that 411A is exactly right in what he says. What would be far more constructive would be to discuss why he is right.
I'm trying to, look-
You could help my learning process enormously,and everybody elses, if you would give a reason why there is a drop in manifold pressure on a supercharged engine with a supercharger doing the same RPM as before the failure.
To my mind,assuming the original scenario where fuel starvation is the cause of the engine failure, the only thing that has changed is the fire in the combustion chamber has gone out.
With no hot gasses being forced out of the combustion chamber and with a bit of valve overlap, it is feasible that the back pressure on the inlet manifold is reduced causing a drop in MAP as Werbil said in an earlier post.