Personally I've had two rx7s (one s4 and one s5) with no emissions AND exhaust and they were fine... even with the 6 ports removed on the s5. You don't have the airflow to need 550s even in the secondaries. It's just not necessary. Fix the
REASON you are going "lean".
BTW, have you taken an english class in your life? Punctuation and complete sentences man!!