97 GMC Jimmy running bad

So last fall I had a tune up done because my truck was running bad. Going down the road at about 2300 rpms or so you can feel it chug or like jerk back and forth and if you look down the tach is moving about 100-200 rpms as it does this. So I got a tune up, seems to have cleared it up, uptil about a week ago. Head out too work and it starts missing and you can feel cylinders hitting on and off. So I get it checked. Says "Random cylinder misfire, bank 1 cylinder 3 causing oxygen censors to fail. So I get new oxygen sensor and still the same problem. So now Im wondering if its the catalytic converter being plugged or something. If so, can you just cut the catayltic converter out and still have it run good or will the o2 censors being before and after it cause it to still run bad? Or any other suggestions what it could be?

had this with my 2000 blazer... changed plugs and fuel filter... cleaned all sensors... still kept doing the same thing... seems to be the fuel pump... low pressure makes it run lean and farks it all up... check your fuel pressure.

Ok thanks

forgot to ask, but what should the pressure be when I check this

64-65 psi

60-66 psi when running

75-85+ psi when u pinch off the return line