I was having similar problems with my 96 KA 240. It would barely run at idle and seemed sluggish.
I ran a diagnostic tool on it and got P0550 as the code, which comes back as a bad idle control motor. After talking to the tech at the local dealer and learning that nissan does not stock the idle conrol motor in the United States we decided that it was probably something else on the throttlebody that was causing a poor signal.
What I ended up doing was taking the throttlebody off and cleaning the crap out of it with carb & choke cleaner until it was spotless, all the vacuum holes were free and clear of gunk and garbage, and the edge of the throttle plate was cleaned of carbon and what not.
I didn't believe it would work but was I ever wrong, just cleaning the throttlebody made a 100% difference in the way the car runs and idles and even the gas mileage impoved.
This may or may not help you...but it's worth a shot.
Also, regarding the ticking sound from KA24DE's...
There is an upper timing chain tensioner that consists of a simple L shaped piece of metal over top of the timing chain between the cam sprockets. Many MANY times, this part is broken or so badly damaged from wear that it's non-functional. You have 2 choices:
1) take it off...put your car back together and drive away without replacing it, <dealer approved option> My car is currently like this.
2) Buy the replacement part, replace the defective part, reassemble car and drive away. <also dealer approved>
This may solve a great deal of your upper valve train noise.
I am looking for a new upper timing chain tensioner to install, if for no other reason than to see if there is any difference.
Just my $0.02
-Texsilvia