Trying to figure out state of tune with supercharger and FCT1, stumbling at WOT in 2nd and 3rd.

I'm having some minor drivability issues with my Tacoma and I'm trying to figure out its state of tune. There are a few variables I'm dealing with and need help figuring out what's going on.

My main concern is keeping the truck's reliability and durability. The extra power from the supercharger is nice, but I'm not trying to get more power out of it. I just want to make sure it's tuned right.

I'm feeling some stumbling when I'm on the throttle in second and third gear. This has shown up recently (past 1000 miles or so) after getting the supercharger rebuilt.

In addition to this, the truck will occasionally throw a Bank 1 Too Lean code (P0171) and has a catalyst system below efficiency code (P0420).

I've had the P0171 code since I've owned the truck, over 3 years now, and haven't payed much attention to it -- but now with the stumbling I'm more concerned.

Truck is a 2002, 5VZFE with TRD supercharger (stock pulley). It has a Split Second FCT1 piggyback and stock fuel injectors. I'm at around 5k feet elevation and seeing boost around 5psi. The charger and FCT1 were on the truck when I bought it.

I do not have a 7th injector, that's clear from looking at the FCT1 unit. My understanding is that the FCT1 I have is designed to work with larger flow injectors, and reading the service history of my truck, it used to have Ford injectors installed that were causing problems, so stock ones were put back in.

I just took it to a Toyota shop to have the O2 sensors replaced, but they told me that the O2 sensors I have now are giving good data and my cat is on it's way out. They also mentioned that the fuel trims were "all out of whack". I'm not sure what that means yet. They said the trims were around 30 -- not sure if that's positive or negative. They cleaned the mass airflow sensor as well to see if that's the cause of the lean code -- but I doubt it since the MAS has been cleaned a few times now.

I run an ODB2 Ultragauge in the truck to track real-time fuel economy, and it's clear that the real world fuel economy is worse enough that the truck is getting extra fuel from what is being reported at the ODB port.
The truck generally runs OK -- It's the stumbling at WOT that I'm wanting to fix, in case my engine is running lean and is a ticking timebomb.

So I'm considering a few things:
1. Replacing the cat in case it's causing an exhaust restriction or messing up the ECU somehow. What are the chances of this?
2. Replacing the stock injectors in the truck with higher flow injectors, in case that the piggyback FCT1 I have can't get the fuel delivered that's expected with the stockers in there now. What are the chances of this?
3. Taking it to a performance shop to sort out. Might have to do this anyway. But, maybe there's lower hanging fruit that I can take care of first, and save some money, I'd like to try that.

Let me know if you guys have any input or advice, thanks!

 

@1997tacomav6

 

I went stand alone haltech

 

Haltech... haven't heard of that tuner before. Is it a piggyback? What was your tuning process like? Sweet truck, super cool seeing a V6 in a single cab. I bet it hauls ass!

It's inspiring that you've got so many miles on on yours. I hope I get the same. My 02 has 230K on it right now, and the supercharger has been on since the truck was a wee little pup with like 20K miles. Hopefully all the abuse with poor tuning hasn't taken too much life off it

 

I've done some research into fuel mods and thinking of swapping my stock injectors with the 312cc brown top injectors from the 90s Supra, P/N 23209-46031. Anyone have experience with these as drop-ins for a supercharged 5VZ?

Looks like they're $230 a piece from Toyota, but there are way cheaper replacements on Rockauto, like these. (STANDARD MOTOR PRODUCTS FJ389). I wonder if it's worth paying double for the OEM Toyota ones.