First I would make sure your IMRC is still properly connected to the secondaries. Next, try letting it sit over night to cool off and see it they will work when the engine is still cold. If the secondaries are still not opening, you need a new IMRC my friend.
You could try manually holding the secondaries open with some form of a wire tie back or something (sorry, haven't had to investigate this linkage). I would have to believe your car would be a little sluggish down low and may end up killing your fuel economy below 3700rpm. The A/F ratio would lean out with the additional air flow below the normal secondary opening point and the EEC would begin dumping fuel to make up for the lean condition. Just something to keep in mind. Good luck.
