I have a couple questions my searches did not come up with answers for.

I just rebuilt my S5 motor-New housings,Racing beat rebuild Kit,header and I did the Tb mod and replaced all vac hoses and injectors. I now have a little over 700 miles on it--A couple things I am concerned about. It starts imediatly but idles at about 300-400 instead of 750 till it is warm--it doesn't affect anything I can drive right off--I have set the timing and adjusted the TPS and adjusted the screw on top of the plenum all the way --this all could be related to my next problem.
My check engine light will come on if I am just creepng along about 1500-2000 rpm--if I hit the gas it goes right out--it does trow a code-17 feedback system--It did this before the rebuild--would a o2 sensor fix this? the last and possibly the most important is there is a engine vibration @1400-1700 rpm nothing that will make you stop the car--mayby just a Mazda thing? --it goes away above that? the end play was in spec the only thing I have changed that I can think of is that I had the flywheel machined, new clutch

 

Did you replace the engine & tranny mounts with the rebuild? That's a weird range for vibration...

It the S5's are like the S4's, the feedback system will throw a code if you're above 1700 rpms, and the sensor inputs are not what they should be...If you are still warming up when this happens, then the codes disappear soon after, you're OK- it just took a while for the sensor to warm up to operating temp...You could also read the O2 sensor inputs from the ECU while driving (I like to do that, just to see how she's running, fuel scheduling-wise. I know Hailers likes to keep track of his also). If you don't see the inputs bouncing around .5v or so during cruise, you may have a bad sensor...

 

The motor/trans mount are new-I am worried that the flywheel was not machined right? would anything else cause that kind of vibration say fuel inconstancy?

the engine light happens cold and warm never above 2k--I'll look for a NGK o2 sensor--I'm using the bosch universal now. the reason for the rebuild was previous owner maint/over heating and the o2 sensor had to see abotu 100 miles of leaking coolant

also at what rpm's will the s5 plenum change from the low rpm runners to high rpm runners
is it the same time as the 5th/6th ports open?

last thing when you monitor the o2 output are you just sticking a lead into the back of the pin on the ecu? Also I dont have a pin out--where is the o2 imput on the S5 ecu

 

I have read a few posts about running a new wire from the o2 sensor--How important is this wire to be sheilded

 

the tb mob would may be make it idle low until it is warm