Misfire

Ok so Im having trouble again. I just replaced alot of parts now Im having a misfire as my check engine light will flash. Its on all the time becasue of an O2 sensor. My gas milage sucks about 215 miles to tank of gas. It idles rough and will fire right up after sitting all night but if i try to start after sitting an hour its hard to start..
I changed

Spider injector
intake gasket
plugs
wires
map sensor
oil
water pump

Any ideas

Which Blazer and which motor?

oh yeh lol its the 1995 blazer w engine

Sounds like either or both of the fuel supply/return lines going to the spider inside the intake plenum might be cracked. Do your fuel pressure check and see how fast the pressure leaks down.

ok ill check it this weekend but is there a way to check the spider itself It was used when I got it so Im wondering if that could be bad