Suggest you do a Google search for "fuel injector service" shops in your
area. These shops typically charge about $15 or $20 per injector for
ultrasonic cleaning and calibration. Tell them what motor the injectors
are from.

Which 2?
The injectors get their signal to fire from ECU via the trigger points in the base of the
distributor.
There are 4 sets of points. Each set goes to 2 injectors. Usually, oil goes up the dist shaft and
takes out the points.
Your cylinders are 1 to 4 down the pass side and 5 to 8 down the drivers side.
The trigger points fire these cylinders at the same time:
1 + 5
2 + 7
3 + 6
4 + 8

If you are losing any pair listed, look at the trigger points.
There are 2 different styles: with the lead and without the lead.
Up to engine 016343 uses the set without a lead, Bosch number 1 230 090 009
From engine 016344 uses the set with the lead, Bosch number 1 230 090 013  They are not cheap......
they list for $530.00.......

Two reasons that caused my SL to run crappy were: the trigger points on
the dist or the throttle switch....the contacts in the TS get worn out
and start giving the ECM the wrong info