This from the installation manual

"Manifold Gas Pressure Adjustments (Hi &
Lo Fire)
NOTE: Gas supply pressure MUST be within minimum and
maximum values listed on rating plate. Pressures are usually set
by gas suppliers.
Make adjustment tomanifold pressurewith burners operating and
combustion air box cover removed.
Remove combustion air box cover. (90+ ONLY)

2. Connect U--Tube manometer to the tapped opening on the
outlet side of gas valve on the manifold pipe. Use a
manometer with a 0 to 12 minimum water column range.
3. Turn gas ON. Operate the furnace on high fire by using a
jumperwire on theRtoW1&W2 thermostat connections on
the fan board.
4. Remove the adjustment screw covers on the gas valve.
Turn counterclockwise to decrease the manifold pressure
and clockwise to increase.
5. Set the manifold pressure to value shown in Table 1.
6. Operate the furnace on low fire by using a jumper wire on
the R to W1 thermostat connections on the fan board.
Note: The fourth (4th) DIP switch should be in the on
position to set the low fire manifold pressure. (See wiring

You are correct in jumping R,W1,W2 to get high fire, R,W1 for low fire.