If you want to experiment in finding out where the air restriction is occurring, here are a few things you can try. You should try them with the batteries removed, and without loading the bowl.
Unscrew the cap and with the mouthpiece still inserted into the cap, check what the draw is like. On mine, it's almost the same as just breathing through my mouth; almost no restriction at all. If your draw is restricted, then pull out the mouthpiece from the cap, and see if it's the mouthpiece or the cap (or both) that is restricting you.
If it's not the mouthpiece or cap, then put your lips around the top of the bowl (this is why you want to remove the batteries and the load!), and suck, and see how that goes. If it's restricted, then the next step is to unscrew the battery holder, and suck on the top of the bowl again. If it's still restricted, the next step is to unscrew the bowl/heater assembly from the battery-holder to 501 adapter. That's the part with the bowl on one end and the other end screws into to battery-holder. It looks like a single assembly, but the bowl/heater actually unscrews from the top. This is not easy without using one of OF's tricks, as gripping the edge of the bowl and unscrewing is hard. OF suggested wrapping some rubber bands around the part of the bowl that tapers in toward the heater, building up the rubber bands until you can easily grip them, and use them to more easily unscrew the bowl/heater. Or you can use rubber gloves. Just don't use a pliers or similar, or you will damage the bowl. There is an O-Ring around the bowl that you can't see until you unscrew it. If you get this far, then sucking on the bowl again will tell you if the bowl/heater assembly has the air path problem or not. If it doesn't, then suck on the end of remaining assembly that held the core/heater, and see how the air flow is with that part.
This last part (removing the core from the adapter) is a scary thing the first time you do it. And screwing it back in is as well. It's easy to screw it in almost all the way, and everything looks OK, but the electrical connection to the heater becomes intermittent or stops working. So maybe you want to try the other stuff first, and if the air flow problem turns out to be in the bowl/heater/adapter assembly, we can dig up a video or two that you can watch first. Others may have better tricks/suggestions as well. If we can get the air flow working, I suspect everything else will be Jake too.