1998 blazer misfire cyl 1 and 3 consistantly. new plugs wires cap. snap on scanner shows 1 and 3 on misfire.

Use a noid light and check for power to the injectors. Use a stethoscope and listen a bad injector you should be able to hear.
If this doesn't work check compression in the cylinder.

Check firing order on the cap. Wires 1 & 3 may be transposed. Try switching them in the cap.

1 and 3 are together on intake?

Cylinders 1 and 3 are next to each other physically, both on the engine and in the distributor cap, but not in the firing order.

When replacing the wires, or the cap, it's easy to get confused and install them backwards.