Please Help

[mudchaser]

ok so here it is it is a 1997 gmc k1500 sle with the 5.7 a 6 inch rcd lift duel exhaust k&n air intake

all that was done when i bought it with a bad trany

replaced: 460le tranny spider injectors with multiport upgrade, spark plugs cap rotor and wires and egr

it ran great for a few weeks then the tranny started sliping and motor would also bog down (like a cloged cat maybe) so i pulled the codesand got p0307(7cylinder misfire which was the reason why ireplaced the injectors) p1870 trany slippage p0154 and p0155 which were 02 sensors on bank 2 and p0420 a bad cat reading

what i thought change 02 sensors and bad cat reading wou go away since it get the cat reading by comparing 02 sensors?

so i change the sensors and no differents truck still runs the same except no codes have came back on?

i have a feeling its a computer problem because of the new rebuilt trany is slipping one interesting thing the light for my gear indicator on the dash hasnt ever worked?