I just read the first few posts, so sorry if it's already been covered. You MUST MUST MUST tell us more, specifically whether your car is turbo or n/a, and it's good to know series 4 or 5 as well, and do it in the first post.

I would say it's likely that since your car is an n/a, you may not be actuating the fifth and sixth ports, which would cause you to run rich if you go above 3800 rpms. Then again, if you go above 3800 rpms, your gas milage will be bad anyways. Did you buy the exhaust used? is there any chance the catalytics are clogged?
Also, change your air filter.

 

If that's the way you drive your RX-7, you bought the wrong car. Why would anyone buy a turbo car and deliberately avoid boost? Never mind the obvious absurdity of not being able to use more than ~20% of the engine's power; the stock turbo's responsiveness is going to make you a (barely) mobile hazard to other drivers as you accelerate everywhere at a snail's pace. Even Prius drivers would get pissed at you.

I'm struggling to interpret your definition of "better"...

That's wrong, the auxiliary ports have zero effect on AFR. How could they? The ECU determines fuelling based on airflow measured at the AFM. If the ports don't open when they're supposed to, airflow will be lower and so the amount of fuel injected will be correspondingly lower.

If you think that's because that's when the secondary injectors come on, again you're wrong. There is no sudden change in AFR when the secondaries come on (unless something is wrong), so there's a no sudden change in fuel consumption. It is true you'll use more gas driving over 3800rpm than you will driving under it, but that's only because you're going faster. That same is true at any other point in the rev range.

 

yeah, mine runs perfect till u shut it off hot. then it floods, well my 88 t2 ive drove it about 40 miles and used about 1/8th tank of gas. did the exhaust change back flow.

 

Here is a complete stab in the dark, for what it's worth.......

I have a 88 Chevy S-10 which would flood unless I removed the cover for the air filter and otherwise would run very rich. Ended up being the coolant temp sensor went bad, thus sending extra gas in to warm the engine up (because it always though it was cold). Possibly you are facing a similar situation?

 

It's been a whole year. Ya think the guy has fixed his problem by now? one would hope. Dead Thread Resurrection FTW!

 

One would hope, but no, I'm still getting 13/20 city/highway. I've more or less just accepted that for now; as far as passing smog is concerned, that probably isn't happening anymore though...