Blazer has 158,000 miles. oil changes every 3,000 miles. Blazer runs good except when going uphill. SES light blinks then stays on, can't go more than 10-15 mph uphill. SES goes off after couple cycles of new gas. Had ignition switch replaced. Had tune-up. Had PCV valve replaced. Had oxygen sensor placed. Had injector service.
Codes found were P0300, P0151. Any ideas on what to do next? Don't say trade in.

Clean your MAF sensor with TN cleaner and a gentle toothbrush and get the black crud off of the two small sensor wires. BE GENTLE!

Check fuel pressure?

Did you replace the fuel filter?

P0151 = HO2S Circuit Low Voltage Bank 2 Sensor 1

Yes, but the MAF sensor if dirty will cause O2 sensor codes as well.

I was only stating the code for those attempting to help. When I tried to look it up in my Haynes manual, it wasn't in there. I had to do a web search to find it.

I was only stating the code for those attempting to help. When I tried to look it up in my Haynes manual, it wasn't in there. I had to do a web search to find it.

Oh, ok , I see. No prob. Was just letting him know before he swapped it out and found that it didn't fix the problem. ;)