I meant might someone have added a boost controller to squeeze more from the 602.

The plugs can be replaced with the manifold in place, crossover pipe and cruise actuator off. Whether this is the way you should do it is up to you.

Read up on how the injector lines are restrained. Renew any broken or missing clamps if you pull the manifold.

Sixto
98 E320s sedan and wagon
02 C320 wagon