Hey guys i'm having a little bit of a problem. I recently just got my car running and i'm nearing the end of the break in period. The car was tuned previously and i'm currently running the almost same exact setup with the exception of a different fuel pump. downgrade from walbro 450 to an aeromotive 340. setup is a built 2.4l and 6266 turbo setup. made 525whp ???tq on 93oct, 4 years ago... anyways the problem is that under 3/4 to almost full throttle the car leans out as the afr's go to about 14.7-15.xx and i'm not sure why this is all the sudden happening. I have gone full throttle here just recently and it scooted with no hesitation even with the smaller fuel pump. I found a small fuel leak coming from the fpr fuel line... fixed that and went for a drive and its still doing the same thing. I pulled the spark plugs and this is how they look... I am running the denso ikh27 spark plugs. any suggestions would be appreciated.

 

Those super lean AFRs under boost will rapidly kill your engine. Don't boost until you find the cause!

A few suggestions:
1. If you have only changed the pump since it was last tuned, put the Wally 450 back in. While you are in there check the black rubber grommet on the tip of the pump outlet. This sometimes degrades and cracks, or is unseated on reassembly, causing a pressure leak back into the tank.

2. If your car sat for 4 years, pull the injectors and get them cleaned. They could be gummed up.

3. If going back to the 450 and clean injectors doesn't solve it, then you should run a diagnosis on fuel system pressure at idle and under load.

4. If your fuel system checks out, you may simply be over boosting due to the cold weather, which would also cause lean AFRs and breakup under load. Log boost and adjust WGDC tables to compensate.

 

First and foremost thanks for the reply. It's definitely sitting until I can try replacing the pump and see how that goes. Here are my responses to your points since I checked a lot of stuff on my day off. First, I will say that it is very odd since I got the car back on the road earlier this month I've put roughly 400-500 miles on it. I have given it one full blown 2nd-partial 3rd gear pull on the highway and these problems started the very next day after that. I wonder if that was overkill for the smaller 320 lph pump from the original 450 lph pump on the original tune, and its just not up to the task???

1. So the Wally is currently in my brothers 1jz sc400, so I just ordered the e85 version of the pump with the rewire kit and that should be here Tuesday. I did pull the pump that's in it currently and the rubber grommet was fully intact I replaced it anyway since I have extras. The fuel sock was very dirty so I cleaned it as best as I could with brake cleaner.

2. That was the next thing I addressed. I did the DIY method of cleaning them and the spray pattern from the injectors were all perfect. (Not paying 170 to a local shop to check them)

3. I will be giving this a shot if the replacement pump doesn't make anything better.

4. At this point I will probably take it to the local tuner that I know and have him check all that stuff.

some pics of the fuel filter and how nasty it looked

 

That fuel sock looks like it has ingested rust. BTW - That's not the fuel filter. The filter is actually molded into the top of the white plastic fuel pump hanger and cannot be cleaned.

The brown particulates on the towel point to possible corrosion inside your tank. Unfortunately this often happens if a vehicle sits for a long period with a partially filled tank. You should check by sticking your phone in the tank and filming the interior. If there is evidence of rust on the inside, depending on how bad it is you may need a new tank. If the corrosion is not extensive it is possible to clean it chemically. See this:https://www.doityourself.com/stry/ga...rom-a-gas-tank

The rust may have clogged your filter resulting in reduced fuel pressure under load and hence the spluttering. You will need to replace the fuel pump hanger in this situation.