I've been having this problem for a while. My car doesn't like to rev until it gets to around 3800RPM. Once I get past there, it revs fine, but almost anywhere below there, it wants to hesitate severely, along with the occasional backfire. I think it may be a vac leak, but I'm not sure and want to see if anyone else has any ideas. Also, just in case, is there anywhere I could maybe get a set of all the vac lines, seeing as if one is going, I'm probably about due for the rest of them to go. Thanks.

 

Just replace all vacuum lines with silicone. Buy the small guage by the foot, because it takes alot.
I believe the rx7store sells a kit that has all the silicone lines you need.

As for the hesitation: Check to see if your aux ports are working. If one has stuck open that can do it. I had one stuck closed. After that you may want to pull your primary injectors and get them tested or cleaned.

 

I know the aux. ports are fine, since the car acts fine above 3800 rpms. I forgot to mention that the car will sometimes begin to act normally after I've driven for about 15 minutes or so, although it eventually hesitates again.

Edit: realized you said one port may be stuck open I'll check into that

 

I thought it might be a primary injector problem. I know T2's have the problem ( only they hesitate after 3500~3800...not before ) and all you have to do is add an extra ground to a certain pin on the ECU.