Picked up a gem recently, 1985 S model RX 7, 41k miles, Brand new condition, Mikuni carb, aggressor manifold. The low milage is a good and bad thing, it's been in a garage for a long time and I've been ironing out all the problems associated with that. (New fuel filter, Seafoam additive, new spark plugs/cables, adjusted the timing, oil change, etc.) I also added in a PSI gauge on the fuel intake to see how much it was running (6 PSI!!) purchased a pressure regulator and set it to 3.5. Overall, car runs extremely well now but there's still something off.. as stated in the title, it feels like the car runs rich at idle, and acceleration is lagged at revs below 3.5k.

I'm wondering if this is normal just because of the carb or if something still needs to be tweaked.

(Would fuel Octane have anything to do with this?)


Edit: I also re adjusted the carb settings to 1 and 1/8th turn

 

As far as I know 3.5psi is still a little bit high fuel pressure for this carb. Although I'm not positive about that, you might want another reference. Try adjusting it down on the fly. Also, have you messed with the air/fuel mixture screw yet? All else fails, pop the carb open and clean it all out, it may be quite dirty from sitting for so long.

 

Some things that might help....
Is the exhaust still stock?
I'm no Mikuni expert....but what size is the carb?

I'm just thinking if you've got a big carb and a stock exhaust....maybe that's a place to start?

 

It does not appear to be a stock exhaust.. almost certain it's aftermarket.

I have made adjustments to the air fuel mixture until i felt like it was running it's smoothest.

I have not however opened up the carb itself and cleaned it out, I figured the sea foam would have taken care of that but I'll take a look into that..

 

I had similar probs and found that the brushes on alternator were well worn,but it still idled/ran etc but would cut out at low revs and backfire and struggle with a hill ,fuel circuit cleaned etc.