92 blazer 4x4 wont start

i have a 92 4.3ws-10 blazer i just replaced the fuel reg the nut kit andthe injectors were fine replaced the intake gaskets too the when i drove it the ses light came on the codes were 42 & 43 SO I REPLACED the knock sensor and the ECM modual now the spark is yellow and weak and it wont start any help would be great thanks loosewheel

Welcome to AF
Is the spark weak right out of ign coil or end of coil wire?
Check for good 12 volts to ign and coil.
Make sure the coil and ign module and dist pickup coil is good.