I would like to say though that I have been searching for about two months on this forum along with others, and straight up Google searches.
I hope to become an active member of this community and also look forward to everyone's insight. Now on to the problem
After keeping up much maintenance on my newly drivable Z (I've got a 1993 300zx N/A 2+2 Standard Transmission with an imported engine, multiple mods that I can list if necessary), it seems to have hesitation (almost a misfire?) between 2 and 3000 rpms.
I'm not an EXCELLENT mechanic, but I'm learning and have done everything on my own (don't believe in paying someone to do something I could learn to do).
I've performed an engine swap (twice =_=), changed the PCV valves, done all the mods myself, replaced power steering pump, starter, O2 sensors, etc. I'm rambling, but what I'm trying to say is that for the most part, I do know what I am doing, and have resources available to do so.
To get back on topic though, sometimes the hesitation is almost non-existent, and sometimes it is very noticable (when driving between 2 and 3000 rpm the sound is comparable to someone rolling down the back window in a sedan, the choppy-windy sound we'll call it lol).
I have the timing set right on 15 degrees, have gone through many, MANY hesitation/rough idle trial and error type things, cleaned and inspected coolant temp sensors, cleaned the throttle body, checked fuel pressure, unplugged coil packs to check for idle drop, check and set the TPS, checked the MAS. I'm just running out of ideas.
The hesitation really affects the acceleration and I know it used to have more get up and go than this.
As a side note (may or may not be related) EVERY time I start it up (cold start or driving for a few hours) the car bounces between 250 and about 600 rpm for about 25-30 seconds, it then decides to idle comfortably at 1000-1100 rpms. Turning the A/C on/off drops/raises the rpm by about 150-200, but only for about 5 seconds max so I believe that that part is fine.
If I punch the gas when it is bouncing between 250 and 600 it either dies or gets extremely close to it, however if I gradually lay on the pedal, it rises fine and smoothly and when let off the pedal it falls back down to its 1000 rpm.
When it is idling smoothly at the 1000-1100 range, punching the gas has about a half-second hesitation before rising fine. I can hear the intake "gasp" when I step on it, so I know the throttle is opening up like it should. As I said I have cleaned the throttle body well.
Also as stated, I cleaned the PCV valves and that seemed to help some since they were pretty clogged. I have replaced the O2 sensors, but used some from a parts car, they were working fine though when that car was "parked".
And finally, (again may or may not be related), when I do try to accelerate heavily there is what sounds like a belt that chirps at about 3000rpms. Not when I step on the gas, but when the car rises to 3000 it chirps once
. It also does it occasionally when I push in the clutch after heavy acceleration.The slight hesitation when stepping on the gas while idling may be acceptable, and I just don't know how quick the response should be, but the loss of power or hesitation at the rpm range is very disappointing.
After putting the countless hours and money into the car I want it to run right, and know there was a time when it didn't do this.
I really hope to get some insightful answers and get this fixed ASAP. In the mean time, here are somethings I will try:
-Planning to get NEW PCV valves and hoses, rather than just cleaning the current ones.
-I have an AshSpec tuned ECU, and plan on calling them tomorrow (Monday) and seeing if I should have adjusted the timing to something different.
-Check the actual injectors rather than just the coil packs to see if they're actually working.
-and finally (what I may should have just started with) check the ECU for the codes it's throwing.
If anyone knows the answer to the AshSpec ECU timing question, feel free to answer. Also, if someone feels just cleaning the PCV valves was enough, let me know. I do have a service manual if someone puts reference to that. I also do have a parts car and two spare motors with almost all attachments (including the full 12 coil packs and injectors
if someone has something that may require trying different parts.Plz NICOCLUB, help me figure this out!
I asked the Z1 guy about the fuel pressure, he said that he doesn't think the ECU tune could or would raise the fuel pressure. I didn't want to argue with him, b/c I don't know about tuning ECUs, but doesn't it remap fuel and provide more fuel in some cases? Someone please clarify this in case I still am not able to get AshSpec on the phone.
and 53 Exhaust Gas Sensor Circuit (Right). 
