2.0L + 2.1L + 2.3L + 2.4L = 4

What I mean is that you could apply some general engine knowledge to get a rough idea of where each stands. There hasn't been a great following of people to put these engines in other cars, and most stick with the 2.0L for that reason. Basically it means there isn't the kind of documentation you're asking for about power curves and such. What information that is out there is usually already highly modified with a huge turbo, aggressive cams, and so forth. What I am telling you is where the 2.0L stands and where the other engines stand in relation to it.

2.0L Power is mid range and well rounded. Not much to talk about on the low end, and falls off past 6 grand.

2.1L Power is all on the high end, meant for very large turbos requiring long spool times that need the extra RPM. Low end torque is relatively the same or less than the 2.0L.

2.3L An excellent street engine with plenty of low end torque, but sacrifices made in the high end, and lower red line.

2.4L With the most displacement, this provides more than enough torque and the quickest turbo spool.

Any kind of numbers would be a guess.

The G54B is a good engine, but many especially in the Starion/Conquest community envy the 4G63, and are tired of constant problems that arise when seriously modifying the 2.6L.