But what is confusing the issue is this statement:

BamBam
"It did force me to either stomp on the gas to downshift, or to shift to 'D', then back to '3' real fast, to downshift and force it back to '3' again. "

Lockup IS very different than shifting up and WILL happen AFTER the vehcile makes any shift and will feel like a loss of power or slippage. The Interceptor allows you to delay this lockup until you are farther into the powerband of the gear just shifted into. Of course you are in D, it will be more pronounced but has no bearing on the issue of the vehicle not staying in L,2, or 3 - in 2 or 3 the tranny will downshift below the setting but not above.

To test, put it L and drive until the rev limiter kicks in @ ~6500rpm
Then repeat in 2 and 3
It you hit the rev limiter in these settings, then the tranny is NOT shifting up above it's setting.