New RX8 Owner, a few questions =)
 

Good afternoon everyone. I've been lurking around these forums for about a month now and finally decided to register. The community here is GREAT and it actually played a role in me deciding to get an 8. I just got a '05 rx8 m/t and absolutely LOVE it. It does have quite a few more miles on it than i wanted (90k) but it was the first one to pop up around my area that was in my price range in over 2 weeks and i couldn't wait any longer for something else to pop up so i went ahead and got her. I've been reading the various sections on these boards and trying to get all the stickies out of the way so i'm learning more and more about the car but i still have a few issues so i figured i'd ask. I did not get any info what so ever from the salesmen on the history of the car unfortunately so i'm making a list of things that i need to do.

-oil and filter change
-fuel filter change
-ecu update from the dealer
-get new coils / plugs

I already did the oil and filter change this weekend, was very easy. Next i planned on doing the coils and plugs and was planning on going the BHR / NGK route since that seems to be the most popular around here. I haven't searched around for fuel filter replacement, is it something easy i can do at home?

But i've ran into something that might need more immediate attention.

After about 25 miles (before i did the oilchange) i got a CEL and was extremely worried (and pissed off). Turns out it was a p0420 (cat sensor efficiency below threshold iirc). If uncorrected or ignored what possible consequences am i looking at? After a few searches it seems like either my cat is bad or the back o2 sensor is shot. Both seem like something easy that i could do (limited auto mechanic experience but i do work on helo's). Obviously the o2 sensor would be the cheaper of the two but can i elminate the cat by unbolting it and looking thru there?

Last issue that i just noticed this morning, when first accelerating around 2-3k rpm and then when changing from 1st to 2nd around the same RPM i hear kind of a MIC sound. It's not a rapid harsh sound at high RPM's like every thread i could find on here reported, just in 1st and from 1st to 2nd at low RPMs and its not noticable unless you have the windows down and stereo off and it doesn't do it in nuetral just revving. Anybody got any idea what's causing this? I did read that using sub -91 octane or over filling the oil when changing it will cause this but neither of these situations exist. Thanks guys =)

What's your location?
bhr = good choice
Don't worry about fuel filter, unless it is showing signs of wear/ damage.
Check the cat just as you described (pull down and look inside). If damaged, I'd recommend going aftermarket, if you are out of warranty (80k miles in the US).
Then, read this

Good luck

Location is Jacksonville, FL.

I actually had just loaded up that page you linked before submitting my thread, thanks.

The only reason i planned on doing the fuel filter is b/c i was just going thru the owners manual and was planning on doing all the scheduled mainteance up to 90k miles since i don't have a service history of what's been done. I also need to get tranmission fluid flushed and changed come to think of it.

that would be a good idea!
While you're at it, I'd check (and probably change) all the fluids (diff, tranny, oil, brake, etc) if you have the time and means