Not too sure why you would use 10w40 motor oil... And good luck with those Bosch parts. In my first hand experience with Bosch O2 sensors and spark plugs, IMHO they are junk.

Have a read through this:
P0143 - HO2S Circuit Low Voltage Bank 1 Sensor 3

 

i have always used 10w40, in every vehicle i have ever owned. as for the bosch parts, the parts place said the plugs would be better, i do still have the old ac delco plugs and they look new, should i put them back in? the o2 sensors, bosch is the only brand they carry. what brand of o2 sensors are the best to install?
now the blazer puffs smoke when i let it sit and idle for a few minutes, without throwing any codes...it also through a p0146 when i was idling with my foot on the brake coming down a 3 mile real steep, rough hill, under 10 mph....