I cruise my 85' Westy at 4000 to 4200 rpms.  I've been doing this since I
purchased the van 6 years ago.
I've changed the timing to 8 degrees BTDC and it has more bottom end and
pulls better through all of the
gears.  By the way, this is not recommended for aircooled. I've taken it up
to 5000 rpms when I really want to see
what the motor will do.
-----1.9L
---orig motor
---130k on eng
-----manual trans  4.83 diff
-----no problems barely uses oil...
-----all original FI w/ Prestone phosphate free antifreeze
----3 electrode Bosch plugs....not sure of number  (I'll have to pull them
to see)I'msure other members know and will post
-----AC is cold w/ freon and pwr steering working beautifully.

Malibu Tony 85' Westy