Wont go over 20 mph 2002 Chevy Blazer 4.3L

Chevy Blazer

just over 60,000. It had been sitting for 7 years. I have dropped and cleaned the gas tank. Replaced fuel pump and fuel filter. I have also replaced the plugs, wire, cap, rotor and air filter. Then I had to replace the spider injection system since it had sat for so long also replaced the IAC. It will start with little effort and idles around 600. If I give it gas it bogs down i can work the throttle and get it up to 2400-2600 rpm but will not go past that. I drove it up to the gas station and filled it up with mid grade fuel and a bottle of sea foam. Could not get it over 20 mph and any time I got on the throttle it would bog down and try to die. I thought that since it sat so long maybe the muffler had something living in it so I disconnected it and still no change. Then I am at a complete loss on what to do next. I ran codes and had the P0300 after driving it but since I cleared it; it hasn’t come back maybe because it hasn’t left the garage since I don’t know. Any help would be greatly appreciated.

I am thinking a vacuum leak or faulty MAF Sensor.

Mass Airflow Sensor Handling Notice

  • Handle the MAF sensor carefully.
  • Do not drop the MAF sensor in order to prevent damage to the MAF sensor.
  • Do not damage the screen located on the air inlet end of the MAF.
  • Also Do not touch the sensing elements.
  • Do not allow solvents and lubricants to come in contact with the sensing elements.
  • Use a small amount of a soap based solution in order to aid in the installation.