Drop in filter will not cause this in the stock airbox

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Some have suggested an exhaust leak, but I have no clue how that could be a factor... im on a tune specifically for a 100% catless exhaust..

Mostly if your headers have a leak around the flanges that bolt to the engine block. Everything else would just cause a smell or not ideal exhaust sound.

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right, but how in the world could that contribute to the fuel trims?

Remember you have 2 O2 sensors in the header runners so if more air is getting in than what the ecu expects it will adjust fuel trims to try and compensate

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You can always reset your LTFT's by disconnecting your battery or reflashing your ECU, then see how they set themselves over time. You're not getting any CEL codes accompanying that current LTFT?

Well, i do think i may have a header issue(s), (installed by previous owner). Im about to snag a tomei expreme UEL...

heres the header thats on there now: https://www.protuninglab.com/20scfrsubrz4.html

My guess is the gaskets are not seated right or just cheap. Maybe try and order some grimspeed gaskets first before replacing the header.

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The problem with dirt cheap headers is usually the flanges warp. I would try gaskets from remflex. They will seal on really warped surfaces.

https://catalog.remflex.com/


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Hey, I cant help you with your LTFTs, but have a read of the below (if you havent already)

TLDR: OFT tunes are good for between 60 and 90% ethanol. Its easy enough to switch back and forth with an OFT.

I have been running my BRZ on E85 for about 4 years. No issues. But we have garanteed 85% ethanol here.

https://r.tapatalk.com/shareLink/top...ink_source=app



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Yeah the OFT tune is super conservative. I’ve been running for years without a flex sensor. The first time I’ve run into an issue was on New Years when I discovered the gas station was closed. I had to go home and swap cars. Only one chain of gas stations has E85 in my city but luckily they are everywhere around me. I still do road trips but only if round trip can be done on one tank (~275 miles). The only con I personally have is that I only make it about 5 days on a tank. Money wise it comes out a tad cheaper than 93. The cold start issues can be resolved with some small tweaks to the boxed OFT tune which only come into play when cranking.

I've been flashing between petrol and ethanol tunes on my car for the past 6 years, my car seems okay with it. Though a flex fuel tune is definitely worthwhile. Even at just E19, I can feel (and see in logs) power over premium petrol (E10 91).



Last year I finally put together a kit and am currently testing dialing it in. I'm very glad I did. Also an excuse to play with my engine programming and tables again. Very happy with my result so far. Also my E30 MPG's are not far off from standard CA premium petrol.


Here's going from a tank of E30 to E19 after pumping up 7.5 gallons of shell premium CA piss.
https://datazap.me/u/solidone/e30-e1...zoom=1475-2165


Pretty healthy. lol

Nope, 0 DTCs/No CEL. Although, the OFT Stage2+ tune 'mutes' most of those due to the exhaust being completely catless...

I asked about your intake as the obvious causes of weird trims will be an intake which needs to have the MAF scaled correctly, a leak after your MAF on the intake side or a leak before the oxygen sensor on the exhaust side. The OFT tunes were made on cars with e10 so that is not your cause.

E85 is a great upgrade once you have whatever is causing your high trims sorted. The OFT tune is safe down to e60 I believe. The OFT e85 tunes never received the amount of revisions their petrol ones did so from my experience they aren't quite as refined. As long as you take things a bit easy on the first tank after you flash on or off e85 the OFT setup is fine.

Ecutek with flex fuel and a good tune from a reputable tuner will be more convenient, have better drivability and potentially be more optimised to your header BUT will definitely be more expensive and can't be resold like an OFT can.