Took my 18k mile 2005 350z for a simple coolant flush at dealer. They joyrode & beat the crap out of it for 35 miles!! When I picked it up it wouldn't start & had a check engine light. It came in fine & they broke it so bad it wouldn't start & CEL!!???
I just got out the military & have PTSD. I CAN'T get angry in public. They claimed it was fine before I arrived but didn't bring it out like all cars after service. It just came in for a simple coolant flush because I was moving from Oregon to Az. They pulled the code & it said cam sensor bank 1. This car was fine coming in & has never had any issues. I just put my hands over my face & told them to change both banks & they CHARGED ME! SMH.
I got to Bakersfield & stopped for gas. When I got back on the freeway my car had lost all power. The car will rev & it will even go 100 mph, it just takes 5 minutes. It takes about 12 seconds to get to 60. It's running fat. If you try to give it has hard it will get 7-8mpg. The exhaust will glow with all the unburnt fuel. Oil is fine & idles normally. Just lost all pull/HP/TQ. I changed plugs, crank sensor, tightened grounds, new optima, cleaned MAF with MAF cleaner but it looks new. Checked the can sensors. Reset ECU by unplugging battery overnight.
I am thinking maybe ECU or TB because I have no engine light or codes. This is a base model so it only has intake VVT. I also thought maybe an issue with the VVT.
I have no idea how to trouble shoot this. I am an aircraft mechanic & can usually solve problems before shops do but I am STUMPED. PRIMARILY, because the Nissan dealer won't tell me what they did to cause the initial problem & won't fix it claiming they aren't responsible.
Any DE gurus out there lend me a lead? Thanks guys! I am desperate. My car has sat for a year. I bought the new '16 Mustang GT but prefer my Z

 

I would check for a vaccum leak or loose air intake. Sounds like you are leaning out and the car might be dumping too much fuel to compensate.
Did you change the cam sensor or just the crank? When I had a problem with my #1 cam sensor my car wouldn't start sometimes and fuel economy had dropped.
BTW welcome back stateside. Fellow disabled vet here. Keep you chin up bro I am sure everything will work out.