My personal 87 MT Westy has had 7 different Subaru engines in it in the last
year.  1 SVX, 1 EJ22, and 5 EJ25's. I have tried numerous intakes, exhausts,
tires, etc.  I have a 1.14 3rd, .70 4th (very tall), 16" Michelin Hydroedge
tires. No roof racks, no side awning. I was getting a consistent 24 MPG with
all the EJ25's, at my normal 65-70 mph.  I made a couple of other minor mods
recently.  I just drove to West River Westies, then through the mountains of
VT and NY for 4 days.  1000 miles. 2 tanks of gas in the mountains 30-65
mph, driving very aggressively, and 2 tanks of gas on the interstates, going
65-70.  Results:
23.8 and 25.0 mpg in the mountains.
25.9 and 26.2 mpg on the interstates

No AC, windows down also.

These numbers are GPS verified/corrected.  No, you won't get this in a
knobby  tired Syncro Westie at 85 mph, carrying 4 kayaks on the roof.
     The mileage has been extremely consistent through all 5 EJ25's before
the current changes.  I would expect the same by swapping a different long
block.
     The EJ25 handles the tall 4th fine.  70 mph is 3200 rpm instead of the
stock 4000.  The taller gearing only accounts for about a 2mpg difference
but makes the driving quieter/more relaxed.  You still downshift on big
hills, but only 1/5th as often as a WBXer.  Most hills can be pulled in top
gear easily.  Really steep, tall mountains can be climbed in 3rd at 55-65 mph.
     There are still 1 or 2 minor changes I am going to try.  I should get
to them in the next month.

     John
     East Coast Vanagon