Poor performance, low speed hot engine 03 Baja

[PTvern]

Nice tight JDM engine, runs fine cold and cruises easily 65-70 hot but runs poorly from stops and at low speed. New O2 sensor upstream made NO difference, Someone suggested MAF but if this 03 Baja has one I don't see it. Any thoughts out there?

 

[2004OutbackSS]

Check your radiator, they start to get slow leaks around 10 years old, will look like blue deposits between plastic tanks and aluminium core. Also make sure your primary fan is coming on at the correct temp, mine was not, still worked with a 12v switch override, but wouldn't take commands from the ecm.