Keihin Power Jet not like the original TZ power valve?

The beat up 2000 YZ250 I just acquired for the motor has an aftermarket probably chinese Keihin that does not have the power  jet or solenoid in the carb. The connectors are there.  
From what I've read, the original Power Jets added fuel to the top end for the TZ rr bikes from @9,000 to 13,000 rpm. It kept the engines alive for the full race. 
From what I've read, the modern Power Jets (at least the 99-00) model, actually closes & leans it out in the upper rpm's, if what I read is correct.  I'm pretty good at tuning Keihins & since it will be a street bike jetted pretty rich, I don't think I want the Power Jet anyway. Am I understanding this correctly?

Yes it squirts additional fuel at lower throttle openings to smooth out the transition from pilot jet to air screw to mainjet, acting like an accelerator pump on a 4-stroke carb. Many people prefer them. They make jetting down low easier, provide a little more low to mid HP and smooth out the dyno curve.