RomRaider

One day boosting along i was watching my wideband and say it blip up to 14:1AFR. which immediatly made me let out of the throttle. tried a couple other runs and same thing would happen when i would reach target boost and then it would smooth out to my target(kinda) AFR. so here are a couple logs, I logged the stock o2 sensor just to see what was going on there too. I think it may be an exhaust leak. but I'd also like another opinon.

in the 1st log there is a small lean blip at around 4000rpm. in the second log, you can't miss the lean blip. i was thinking if my car was running THAT lean, it would have asploded by now.

I think your WBO2 is going out.

It's not an exhaust leak. At 200 g/s, an exhaust leak doesn't affect your AFR.

that was another thought, this is my 2nd sensor. I don't remember how long ago i replaced it either. Thankfully i get them cheap from VW. i'll give it a shot.

anyone else?

My first thought is to recalibrate your LC-1. Do your LC-1 and front O2 read the same when in CL? It looks like there is some difference in their readings in those logs.

My second thought is that I don't see how an exhaust leak would be RPM dependent.

It's a strange "problem".

I want to say that your statement is false. I had a guy that had this same problem. His afr would hit 12s at boost onset and slowly drift up to high 13s and low 14s at wot. He had just installed an alky kit. I thought it could be sucking in air from a crack in the alky line to the pump from the tank since his tank was way back in his trunk. After that was not the case I pulled the exhaust and found a crack in the header collector. New set of headers and the problem was gone.

It could also be the wideband going bad. I would check that before I would go pulling exhaust parts from under your car.

i would think i leaky header/exhaust parts would make my long term fuel trims go alll weird too. I have calibrated my lc-1 twice since the problem started. i would also think a leaky header would make the readings on my front o2 sensor do the same things as my wideband. i'm still going to be sniffing for an exhaust leak while i get a new WBO2

A leak in an alky kit would cause a rich condition under boost because the leak would be post maf. Just a thought but check that your fuel pressure regulator is hooked up. I've seen cars go way lean under boost when that pops off, including my own.

Yes it would go rich if you where leaking boost around the alky nozzle. Have you ever sucked on a straw with a crack in it? You get a lot of air mixed with your drink. Once that goes through the pump and gets pressurized to 150psi it gets injected with the alky into your engine. You will be in open loop and wouldnt see any fuel trim corrections. Your front 02 may or may not see it because of the accuracy of the front 02 at wot is not that great. It may though.
I personally havnt seen this type of problem. And dont know if the pump would have enough negative pressure on the line in to the pump to take in air if there was a crack in the line. Just a therory I had with the problem I was working on at the time. Remeber I said the tank was in the trunk and the pump was under the hood. Go figure!!!!!
And to the op 06rexwagon is right about the vac hose on the fpr. It will cause you to go lean also.
Seeing as the OP doesnt have alky this post has gotten off course!
Now back to the OP's problem.

Took a look at my FPR signal and all is good there. Had a dyno day today and confirmed that my AFRs are still spot on and my WB02 is probably flakey.

I have given this some thought and I don't see how this would work.

At 200 g/s, the exhaust gas back pressure is significantly higher than atmospheric pressure. I just don't see how air is going to get sucked in. I have seen cracked exhaust manifolds and their datalogs. They only had lean fuel trims at low MAF. AFR learning D and trims at WOT have always appeared fine. It might depend on how large the crack is.

In any case, I have not seen this happen.

Also, the OP is showing an AFR of 20.3 at WOT which to me indicates the WBO2 is going out.

Yea, it doesnt sound right but it did happen. Took about a week of taking stuff apart and putting back together. Checking this and that. Finally as a last ditch effort I pulled the headers and uppipe and bingo there was a crack in the collector. All I can figure is in between the pulses in the exhaust it would take in just enough to through the wideband off a little. I dont know!

Go into innovates software to make sure it has a gasoline AFR selected. I had problems with it reading rich but erratic and it was on a custom setting with a random number in there. I don't know where the problem occurred but it happened without ever opening Logworks or LM programmer. Before you replace the sensor give that a shot.