2000 Maxima- Work done, still lagging Please Help!!

[jsta22]

I posted previously all the work Ive done on this car (164k miles by the way)
New PLugs (1 Yr ago, NGK Platinum)
all New Coils (1 y ago)
new bank 2 precat, and bank 2 post cat 02
alternator
Knock Sensor is Simmed with a 470k resistor.. (i hear i need a 550k)
checked for bad/leaking vacuum lines (none so mechanic says)
not to mention, Brakes, Sway Bar links, Tie rods, alignment (which still doesnt feel right)
Radiator,
But the big one, was the MAF sensor, 3 times! Finally getting the ECU reflashed this past time by Nissan with major differences..
My problem is, it has better acceleration and pick up, but under normal acceleration (not WOT or light Throttle, it Lacks that VQ growl.. Funny this is, It has it sometimes, and other times it doesnt.
What Ive noticed last night, Getting onto the highway, I stepped on it about 3/4 throttle,, and it had growl, and took off like a champ! RPM easily pulled up through 5-6k RPM..Like I know it should! was only driving at the time, for about 5 minutes so far..Felt great all the way to Lacrosse Practice.. About 35 miles away.
On the way home after 2 hrs, different story.. getting on Highway, Engine lacked that growl.. and struggled once it got to 4k RPM.. would jump up quick to that, then lag in pulling past that, no matter what speed I stepped on it, 40, 50, 55, 60.. 4k RPM seemed the wall...and engine seemed less powerful and lacked that muscly growl..
Any Ideas??

[jsta22]

also, If this helps any, When I first start the car in the morning.. It idles strong, like its supposed to, then almost as if something kicks on, like a sensor or something, and the Idle gets weaker.. Then back up to a strong Idle, and minute later, whatever it is kicks again, ad it idles weak again..

[ZELsJ30t]

Check the maf connector clean wit electrcal cleaner allow to dry and reconnect it make sure you hear it click wen reconnecting this should fix it