recently got a p0134 code along with a p0171 code when my Service engine Soon light came on, I changed my o2 sensor and replaced my fuel pump with the Walboro 255 pump on my stock 03 evo 8 and now The car idles terribly and runs poorly no boost or power. Im going to switch back the stock fuel pump back in but the question is could this be attributed to the fuel pump?

Thank you for the input in advance.

 

big boost leak

 

Swap the pump back.

Then you'll know.

 

Unless you got a bad brand new fuel pump, that is not your issue. A new O2 sensor should have fixed the P0134. The P0171 could be vacuum leaks, which could also be a boost leak, causing the car to o run well. Or you could have improperly installed the new pump.

 

when I had it on the ramp and initialy started the car the idle was so terrible the engine was shaking as well as the whole car I reved it up to 5k about 10 times after 12 mins of warming then the car ran great, great response good power but later after getting gas and parking it on the street I decided to turn the car on again that's when the symptoms came back.

I will check the intercooler piping again since i did have to remove some for the o2 sensor install,
Thanks ppl I appreciate the input

 

If its on mass air flow it sounds like a leak. Unmetered air makes maf cars run like crap.

Do you have a wideband?
Do a fuel pressure test

 

Do you have a wideband ? Do some logging and post up a log please.

 

Are you putting bigger injectors/ turbo in later that you need the 255? Sounds like rich startup problems agree need log.

 

Also, make sure the screen didn't fall out of the MAF.