Why is my 1998 chevy k1500 4x4 5.7 not hitting a ping gear and sputtering?

i have a 1998 chevrolet k1500, it will not kick into a ping gear and it sputters real bad, going up a hill i have to manually shift it to make the RPMs rev up get enuff speed to get goin, i changed the plug,wires,cap and rotor, new distributor, one thing i am thinking is i took the truck to the shop and had them cut the exhaust off to run true dual straight pipes, they took the cats off and unplugged the o2 sensors on the exhaust, so i have no o2 sensors on the pipes... would my pipes the way they are now have anything to do with the way its running or is that the main problem?. i have tried everythingfrom filters to ignition problems and still nothing, buta freind of mine told me if i dont have o2 sensors that that would be a big problem?