Turning needed with test pipes?
 

Am planning to go for tomei test pipes would be necessary to get a tune? Am not a tune expert but I've read somewhere about AFR that playing with the stock cats affect this AFR is that true?

Currently u have a a nismo s tune exhaust and tomei Y pipe.

Thanks

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The only way to know if it’s absolutely necessary is to review some logs. Regardless, a tune is good idea if it’s done well.

I drove for a year with FI HFCs, catback, and gen 3 long tune intakes without a tune. You don't *need* a tune, even if you drive aggressively. You just won't be getting the best performance out of your setup without one.

Swapping out stock cats for anything else would be a reason to get a tune, but if you've got more modifications planned, I would hold off until they're all in place and you're happy with them.