When Gernby e-tuned my car, I had a test pipe with my Fujitsubo exhaust. I’m now looking to replace the test pipe with a HFC. No other mods changed. Would I be ok running the same tune with HFC or a new tune is a must?

 

You should get it retuned.

 

I would do a boost leak check before a retune aswell

 

A tune-up is a good idea to get your AFR in check and to make sure there’s no knock now that you’ve introduced a restriction that you didn’t have before.

You can usually run slightly more ignition timing with a test pipe. If your tune was aggressive, you now might knock somewhere in the map where before you didn't.

 

Thanks for the feedback. It sounds like a re-tune is the way to go.