Gas filler seems to be damaged. Gas will not go in at the regular rate.

Octane ratings have nothing to do with fuel economy or power. The octane rating only indicates how much the fuel air mixture can be compressed before it ignites without the spark plug firing in a hot running engine. Some really high compression engines require higher octane fuels so they don't knock when running. If you don't have a sticker under the filler lid that says you have to use one of higher octane fuels, then don't use high-test.
It used to be that using a low octane fuel in an engine designed to use high octane fuels could damage the engine.
Nowadays, engines are all computer controlled and most high octane engines will re-tune themselves on the fly so that they don't knock if the wrong grade of fuel is used.

a suggested have the filler and recovery and evap system of the tank filler tube checked out ..could be perished seals or piping
other thoughts
some gas stations fuel pump sniffers can be more sensitive to shut offs than others....the pump sensor is supposed to be tested adjustable or sensor replaced regular intervals
these days the operator wait till there enough complaints before doing anything

the new model cars seem to have more filler neck filling issues
than in the past
could be the smaller diameter of the pump nozzle

could be the temperature of the day fuming the gas in the cars filler tube

If you replaced the cap, I would say that you damaged the filler pipe, or vapor recovery line.. It is allowing air to get in the system, This system is pressurized. You may want to inspect that. Your filler pipe may be gone at the tank itself. Have a closer look and smell as you are under there. Also look for any wet spots. Good luck. Please rate solution. Cheers from Nova Scotia!!

on most applications its a direct hose clamping and thats the seal. Never have I heard of a gasket on the gas tank or in the gas tank

After researching this for a lot of vehicles is this:

A ventilation line or the filler hose/neck/tube has possible damage. The only way to know is to drop the tank and inspect the lines going to and from the gas tank to the filler neck where you put the fuel pump nozzle in. If the neck has not been installed correctly, i.e., is twisted or dented/bent, this will cause the problem you are having.

If you can drop the tank and inspect these items, let us know what you find.

Best way to check is by looking at the gas cap. If it does not say "Premium fuel only" you should be safe. Higher octane rated fuel is used for higher compression motors, and I dont belive that your engine (my guess is the 5.4 V8 should be around 9:1 compression) needs the high octane.

Hi: Canister you thinking about is located behind L rear bumper end cover. Won't have anything to do with Blazer not taking gas though. If you look behind the filler on the rubber filler pipe you should see a small rubber line with a black breather on top of it, that is what lets air out of your gas tank when filling vehicle, check it to see if plugged or damaged. Hope this helps. Please rate suggestion... ty

have toyota or any machanic check the filer in the gas filler tube.

Are you going to get a new one, or a junkyard replacement?
You have to take off the rear left tire. Secure the car with jack stands and chucks. There is a plastic cowl on the wheel-well that covers the filler tube to prevent road damage. Take it off. The filler tube is attached to the gas tank through a rubber connector hose (tube) adapter, secured to the gas tank and to the filler tube by hose clamps. Loosen both clamps.. You should replace the rubber connector, as it has been there for many years, and rubber degrades. Loosen about three or four bolts along the filler tube that attach it to the car body. The top part, by the gas lid, comes off easily, it's just a plastic dam. You have to carefully work it off the (other end) at the rubber hose connector. Once it's out, get the hose connector off the gas tank neck.
With the new filler tube, reverse the process. Getting the hose clamp tight over the gas tank neck is hard. Make sure the clamp is seated properly before tightening.
Good luck!

Assume you damaged the gas tank. If you broke a line or filler neck this won't work.

Raise vehicle (safely) and clean tank - careful not to spark - NO GRINDING. I use regular sand paper. Find the hole - sometimes takes a bit of looking. If small, here is an old trick: rub the corner of a bar of soap over the leak and if done correctly, it will stop the leak (no, you're not done). Clean the area around the leak a little better - still careful of sparks. Get some epoxy that will stick to metal wet with gas (from AutoZone). Seal the hole with this epoxy and you should be good. Work quickly - the working time of the epoxy is less than they say it is.

good luck.