Voyager runs rough between 40-55 mph

I’m puzzled.



I have a 2000 Plymouth Grand Voyager with 90K on the 3.0 liter engine.



It started running rough and missing, so I took it to my mechanic. We did a tune up, but that didn’t help. He found a leak in the intake manifold, and we fixed that. Still nothing. Code said it was missing on cylinder 2, so we replaced the injector.



The thing still runs like garbage.



Someone mentioned it might be a bad EGR valve, but nothing comes up in the codes. My mechanic says we need to replace all of the injectors, but I have reservations that such a specific problem would be caused by bad injectors. At low speeds (under 40) and high speeds (over 55), and when I “gun it” through 40-55 it runs better. Not purring, but not nearly as bad as when I give it normal acceleration between 40 and 55.



Anyone out there have any idea what could be the problem?

Someone else told me it might be the mass airflow sensor…but when I called NAPA for a price, they told me my van does not have one! (???)

As you can tell, I’m pretty clueless, but I have faith in you guys (and gals!) to help me out.