[lfalzarano]

You should encounter a stumble attempting full throttle at the lower RPMS you describe.

When these parameters are met: Coolant and Oil Temperature is 68F or above and System voltage is 10V or above Power Key on, and NO SES Codes, the ECM will signal the ports to open and wait for .5 second before turning on the secondary injectors at specific throttle vs, RPM. As the secondary injectors share the same drivers as that of the primaries, the pulse width signals are halved when the secondaries operate.
As shown in the diagrams (below), there are three different styles of driving which will operate the port throttles:
1. Ref. line A-B. Constant throttle position with a rising rpm. At the point the arrow crosses into the 'Port Throttle Opening Region' (top left shaded area) the port throttles open and the secondary injectors start firing.
2. Ref. line C-D. Constant rpm with increasing throttle position - logic as above.
3. Combination of the above: i.e. increasing throttle and rpm - logic as above.

The TXT attached file has the graphs of Throttle Position vs. RPM

My 90 stumbles slightly when I put my foot to the floor below 2000. Hope this helps.