At least with the 1992 500E and 1993 500E/E500, we're talking about a measly 7 HP and lb-ft difference in power and torque. This is, in real terms, a negligible difference and can easily be compensated for in terms of driver skill and so forth.

In terms of a 1/4 mile time or 0-60 time, 7 HP isn't even going to make the difference of 1/10 of a second, taken by itself.

On the 400E/E420, the later cars did indeed have a higher HP/torque rating than the earlier cars. Exactly the opposite of the early and later 500E/E500.

Cheers,
Gerry