Hello Everyone,

I could really use your help with an issue I am having, well a couple of issues actually. These could all be related but I am not sure. I have a 1997 Z28 with the 5.7 LT1 motor, I have rebuilt the whole motor and have added the following Mods:

CC503 Cam
1.52 Comp Cam Roller Rockers
Hooker Shorties

Heres what is new:

CompCam Chromoly Push Rods
Rebuilt Short Block .30 over
Reconditioned Heads
Stock reconditioned fuel injectors
CompCam Lifters
Rebuilt Transmission 4L60E
Mail In tune to specs

Here is my issue, I am getting the codes P0174 and P0171 advising I am running lean in both banks. I am also getting a flat spot when going between 55-60 mph and it only seems to happen when warm. When going in reverse my idle is odd like it is going up high then down low, same happens with it in drive sometimes like it tries to jolt me forward when I am on the brake. I can hear a small leak that I am not sure where it is coming from. I originally had a leak at the flange on the driver side that I fixed by replacing the gasket. I had a loose header bolt that was a nightmare to fix but was able to get a 5/16 head 12 point bolt to get it tight. I still hear a leak and have no idea where the hell it is coming from, but it sounds like it is on the drivers side. Could this cause the issue? Heres what I have done based off research on the forums and web:

Replaced PCV Valve
Cleaned the MAF
Cleaned the MAF connection
Fuel pump assembly is brand new
Checked for Vacuum leaks and cannot find any (EGR is unplugged but was told this wouldnt do anything since Emissions have been tuned out)
Replaced the TPS and cleaned connections

What can the issue be? I am at a loss and cannot think of anything else to do. I never had this issue prior to the rebuild. If the leak is the issue what can I do to find exactly where it is coming from?

Thank you for your help, please let me know if any information is needed

 

The leak upstream of an O2 sensor will cause issues like you are talking about, or bad O2 sensors. Get some AC Delco O2s, or Bosch (people say they have had issues with Bosch but mine have been fine for 6 years and I havnt personally seen issues on anyone I knows cars). I'd get those leaks fixed first, new o2s, then datalog it to send back to the tuner and most tuners wil adjust it for free, as long as you didn't change cam or heads within a year from original purchase.

 

Leaks before the front O2's will cause problems and also if the O2 is very close to the collector and there is a leak at the flange, this will cause problems also