forgive me, I had a long night...
Have you checked your cat?
6K rpms is around when the apv(alve) opens. There is a thread on how to test it.
Also, you may have a fuel pump issue.
Check these three areas
GBNF --'86 RX7 GX RIP | '88 10th AE T-II RIP | '05 RX8 Ti Grey SOLD--
'07 RX8 GT Phantom Blue Mica
Mazdaspeed || BHR || Enkei/ Falken || AFE/VooDoo || Cobb || Lo-Tek/Prosport || Tein || Racing Beat || KEI || Buddy Club|| XCarLink || Redline/ Lucas