K12 has weak acceleration

[Zweli]

Hi guys my car once overheated, had the radiator, cylinder head and block sorted out but the car also lost power. it displays the engine light and i changed almost every sensor, the accelerator pedal, tried a new computer box, a new air intake cover, new computer fuse box, new throttle, but still the problem persists. fuel system also works fine. Once, i tried trouble shooting the throttle body to see if it would flip when i switch the ignition key to ON but it did not respond. I'm confused because a lot of people have had suggestions but all haven't worked out.
Some people think it could be the piston rings, that loses compression but its unbelievable because they were changed as well. my suspicions is with the electrical wiring between the throttle and computer box. Another suspicion could be with the lambda sensor.
These are the only things i havent changed.

Please help?
What really could be the cause of this powerless acceleration?
could the lambda sensor, and piston rings possible be responsible for this?

 

[Mach1]

I assume your car is petrol? check the compression of the cylinders, overheating can cause problems with the bores and pistons/rings. Its a simple test to perform to rule out this.secondly fuel. My advice would be to have the fuel flow rates monitered on a rolling road with a specialist tuning firm if you feel the car is worth investing in.

 

[Zweli]

I assume your car is petrol? check the compression of the cylinders, overheating can cause problems with the bores and pistons/rings. Its a simple test to perform to rule out this.secondly fuel. My advice would be to have the fuel flow rates monitered on a rolling road with a specialist tuning firm if you feel the car is worth investing in.

cylinders are fine,... actually i took the car for diagnosis and all sensors had errors, it gave the following errors P0135, P1122, P1123, U1000 to name a few, i had changed the sensor prior so i dont understand what the problem could be,... my suspicion is with the harness

 

[Mach1]

I think the U1000 fault code may be the most important, you will need an advanced level scanner to communicate with the system control units by doing a system call to determine which of the sensors are communicating and which ones are not, this will help to determine which sensors are playing up and help you narrow down your problem. Nissen will have this equipment or a good diagnostic firm, then again it may be wiring/ connector problems, earlier in the year I removed all my sensors and cleaned the connectors and fuses as they were starting to oxidise.