Like the title says its running lean. At vtec its right around 14 flat and it drops to about 13 flat at redline. Also sometimes it runs even leaner than that for no apparent reason. I am stock everything except test pipe and borla exhaust. I used the largest recalibration kit vortech had 11 or 12 to 1 I forget. I also picked up a comptech fmu and the problem was even worse with that. I thought maybe my fuel pump was getting weak so I installed an extra 255 I had kicking around and I had the same exact problem. The other thing thats interesting is I was getting close to the same afr with a 8 psi pulley in so it seems like its not a fuel pump issue. Any suggestions besides going with ems?

 

Go with the stock cat, it should help richen you up a little.

 

Did you adjust the Comptech fpr? That should have solved your issue if it was a fpr problem. VT fpr is quite lacking without an external fuel adjustment like comptech. Fuel pump issue would be the next logical conclusion unless you have a fuel line kinked somewhere.

 

I understand the cat should richen me up but that shouldn't be the issue and id rather not just bandaid the issue. I did have the comptech maxed out but it had the same issue if not a little worse. I thought for sure it was a fuel pump until I installed a new one.

 

So the problem is much better now. I did the fuel pump mod and it seems to be working much better in fact ive been seeing low 12's and the occasional high 11 right before redline. Its also interesting that at about 6500 rpms it seems to have a nice af spike to almost 14 then drops quick after that. I also noticed if I am in lets say 2nd at 6k rpms and stomp the gas it almost always spikes much higher than id like but quickly drops to 12.6 to 12.3 at redline. If im in lets say 3rd gear at 4k rpms and stomp it it drops into the 12's get a small spike around 6500 and by the 9k rpms I am 12.3 or lower. Seems pretty interesting to me. My next question is this why can so many people run these fuel pumps without issue but I used 2 and both had the same exact issue? Is it that my head and exhaust flows a little better than most? Any ideas would be good it doesnt make sense to me.

 

Which version of the 255 are you running or did run?

 

Only real fix is stand alone ecu, injectors and a tune. I had all the same issues as you for many months. Finally bit the bullet and bought AEM EMS, ID1000cc injectors and a tune and been perfect ever since!

 

I run the gss342 I think the number is its what vortech suggests.

As far as standalone goes I was running aem ems and do not want to go that route again. I would like to keep my setup simple and legal as I plan on driving the car alot more. I think a fix for me could simply be a good pump. If this doesn't cure it I will really consider a piggyback as I am not looking for huge numbers anyway.