My 1993 S10 blazer vortec ran well after I changed the fuel pump and spider injector for a week, but now it's running really rough and rich. I've spend quite a bit of money getting screwed by a mechanic so I'm hoping to get to resolve this on my own. Any idea as to what could be wrong? Any help will be greatly appreciated.

 

Have a go at the EGR valve - carbon "deposits" will cause the egr valve to not be able to close . Poor idle , and hard starts are some of the symptoms You describe .