One difference is the 2.5 turbo wastegate is controlled by an ECU using a vacuum actuator vs a simpler pressure actuator that reacts to turbo output pressure in your '87. There's not a lot online about the whys and wherefores of a 2.5 ECU cutting boost but a popular workaround is to retrofit a pressure actuator. In short, don't pass on an otherwise nice car because it feels low on power. It could be a bargaining point.

Sixto
98 E320s sedan and wagon