Retune after injector swap?

[BrokenProjectGT]

Brief Intro: Bought a modified 05 Legacy GT that was running but had a weird jerking motion when driving it. It also had this issue where if I was parked and held on the throttle steadily, the RPMs would move up and down. No CEL so hunting the cause of this issue has been a pain. I took some logs and AF correction was all over the place as you go through the RPMs. Anywhere from -20 to +20. AF Learning would sit at -7. I did the usual things that are recommended like vacuum/boost leak test, spark plugs, coils but issue still remained. I decided I was going to clean the TB, change the manifold gaskets, swap out some vacuum lines, swap out the PCV assembly, and remove the injectors and have them cleaned/tested.

 

Now this is where I ran into an issue. The previous owner claimed that the engine had Deatschwerks 650cc injectors. I remove the injectors and in one of the cylinders was a pool of fuel. I'm guessing the injector was leaking or malfunctioning. Instead of taking them to get cleaned I went online to find replacement injectors of the same type but couldn't find any reference of the Deatschwerks 650cc side feed injectors being made for my Legacy GT. I ended up buying OEM injectors to play it safe since I'm still learning about working on these type of cars. I'm currently in the process of piecing the car back together. I installed the OEM injectors and just have to reinstall the TB and Manifold.

 

Now here's where I'm a bit concerned. I've always read that when anything engine related is changed on Subaru engines, the car requires a retune. So seeing that the injectors that it "supposedly" had were 650cc's, is it okay to run the car with the stock injectors which are 550cc's? I saw there's copies of the stock tune online. Would it be a smarter idea to load the stock tune until I can get the car retuned? I'm just looking for a little guidance/advice.

 

It was previously tuned with opensource if that helps.

[Infosecdad]

You could pull the existing tune off and check to see what injector size is listed in the tune. That might help answer the question of what it is currently.

 

DW did offer some 650cc side feeds in the past, don't them them currently offered today.

Edited January 6, 2020 by Infosecdad