I have a 1999 chevy blazer and I just recently put in a fuel pump. IT has 224,000 on it and runs great. Recently after I put in the fuel pump and filter I got a code of the car running lean. It called out the mass air flow sensor and an 02 sensor 3. Also, It has started having trouble starting and take a while to finally fire up. Im not sure if this is a cause of the running lean but it also called out a crank sensor after it started having trouble starting up. I pulled the maf and cleaned the hell out of it with carb spray and that helped the situation none. I went ahead and reset the codes to see what it would throw first and I can not get it to throw another code. I suppose my next move is to replace the 02 sensor behind the cat? Any ideas what this could be? Oh and I checked the fuel pressure and it is idling and running fine with perfect pressure.