KevinW

Perhaps the main advantage of 2-BBL offerings was the reduced manufacturing cost. The smaller Q-Jet primaries contribute to improved fuel atomization and are capable of superior economy. A 2-BBL would have higher initial throttle gain because of the larger bores, but such responsiveness is short-lived as the 'advantage' is lost once more throttle is applied, and this setup makes it more difficult to modulate power delivery on take-off. Some packages (e.g. Oldsmobile's 'Turnpike Cruiser' option comes to mind) took advantage of this enhanced initial responsiveness by matching it to a numerically lower final drive; the latter would have been the main contributor to improved fuel mileage, while the 2-BBL would preserve (light) throttle drive-ability in general use.

These carburetors are not troublesome and the OEM unit is the best for this application. This sounds like an adjustment issue. On a cold engine, the choke valve needs to be closed to generate sufficient pull-over enrichment for starting; ensure there is sufficient choke coil tension to keep it closed during cranking after the choke is set (accelerator pumped once to the floor). Also, the fast idle screw should be adjusted to at least 1400 RPM, on the second highest step of the cam, while the engine is at operating temperature. Note that this screw adjustment is very sensitive. I sometimes adjust it a 1/4 turn up or down according to the season, as the factory setting is only needed in extremely cold weather.

The Olds 307 was last used in the 1990 model year. The 'snout' differs on the FWD E-cars. My preference would be to clean the original starter, install a new set of brushes (and address other possible issues), as replacements never quite sound the same, and high quality remanufactured units are difficult to find.

Disc brakes also increase unsprung mass and are more susceptible to corrosion-related failures.

Glad to hear the rebuild went smoothly! It usually takes 3-5 seconds of cranking for enough fuel to reach the bowl. While tightening the fuel nut, the line will often 'wind up' (twists slightly in a clockwise fashion as viewed while standing at the front bumper), resulting in an anti-clockwise spring force that works to loosen the nut and/or filter housing. Instead of over-tightening these fittings, I've found it helpful to pry upwards on the line, where it snakes around the thermostat housing, to maintain a neutral position while the fuel nut is tightened.

The TPS can be replaced on-car, after raising the air horn about an inch. Ideally, a scantool should be used to adjust the closed-throttle voltage, however, the acceptable range is quite broad, plus the software threshold is dynamic and can be reset by interrupting B+ to the ECM to clear the long term memory. If the air horn gasket is not damaged, it can be re-used. I wouldn't expect any significant throttle shaft wear at 100K, and in my experience, electronic Q-Jets don't seem to exhibit the typical minor fuel bowl leakage problems like the early models (i.e. hot restarts don't require a longer cranking period to clear excess enrichment). Generally, rich running during closed-loop conditions will eventually set a DTC 45 (the mixture remains richer than stoichiometric despite the best efforts of the C-3 system), and if this condition is exclusive to open-loop, I'd look at the front vacuum break adjustment, assess the vacuum break's diaphragm integrity, inspect the choke coil and associated parts for binding, and check the hot air tube for any obstruction. A 'heavy' float or deteriorated inlet valve will cause rich running under all conditions due to a high fuel level in the bowl.