I have an '01 Pathfinder, 3.5L motor, stick shift, 91,000 miles.  About
24,000 of
those miles has been towning a 2000 pound boat trailer.

The last few months it's been loosing power as it accelerates between 4000
and
4200 RPM, then the power comes back but maybe not 100%.  It's most noticable
in second gear, where it happens most of the time, but not always.

I've changed fuel filter, plugs, and air cleaner.  I've run 8 or 10 tanks of
Standard/Chevron premium
with Techron, thinking the Techron might clean something out.  I normally
run Shell premium.  The
problem persists.

I have an AutoTap.  It shows that above 4000 RPM, the engine goes from
Closed Loop 1
mode to Open Loop 2 mode.  The Nissan service manual says that Open Loop 2
means
"Open loop due to detected system malfunction" but doesn't give a hint about
what the
malfunction might be.  No Service Engine Soon light, except that about two
months after
it started happening, I got an SES, and AutoTap read out code P1135, which
the Nissan
service manual says is "Left intake valve timing control".  I followed the
check out procedure
in the Haynes manual, found nothing, and cleared the code.  I presumed it
would promptly come
back, at which time I planned to switch the sensor left and right and see if
the problem
moved.  But it never came back.  ("Left" does mean US driver's side?)   My
feeling is that
this was unrelated to the loss of power.

Any ideas?

Chuck Tribolet