Brian,
When you took off the ALDA, did you also plug up the line? I am not saying that the ALDA itself necessarily controls low end RPM, what I am saying is if it is leaking pressure, then that is affecting some other part that does control low RPM power. In fact, it even will affect the shifting of the transmission. As soon as I sealed up my ALDA, it had really soft shifts, I am assuming that the pressure leak affected the vacuum, and the previous owner had his mechanic adjust the trans modulator to soften it. Try unplugging the line that went to the ALDA, and tell me if you lose low end power, and see how much your shifts firm up.

__________________
87 300D - Running on Veggie oil; 260,000 plus miles; Original #14 head