I'm wondering if anyone in this group can help me.  I have two
neutered male cats, one 14, the other 9 years.  My problem boy is the
younger cat, Smudge.  Ever since he was a few months old he has
exhibited strong marking behaviour - which is odd because he was
neutered at 4 months, and the other cat, his role model, virtually
stopped spraying after he was neutered, as near as I can figure, around
2 years.  That was long before Smudge came on the scene.

The territorial spraying is bad enough, but it is compounded with his
peeing behaviour.  When we babysat a neighbor cat for a few weeks at
our place, he used to pee on her stuff - a catnipped stuffed toy
mouse that came with her, literally SOAKED with urine, yuck. (Yes, I
caught him doing it).  So I know that he occasionally uses peeing as a
form of marking.

Finally - probably the worst problem since it occurs the most
frequently and is the hardest to track and clean - his general
urination behaviour.  I doubt very much that  this is marking, although
I could be wrong.  I should mention that he is a highly inquisitive
cat, much more so than any other feline I've owned (his parents were
barn cats, and I should have known better than to take an animal with
this background).  He used to follow me around when he was a kitten
(still does although not to the same obsessive degree) and watch me
like a hawk.  For example, if I put some bread in the toaster, I had to
be careful not to turn my back or he'd be on the counter sticking his
paws down the toaster slot to find out what I'd put in there.  As a
result of his constant observation of me and sometimes imitation, he
taught himself to pee in the toilet. (No joke, no  troll...) I've
seen him balanced on the toilet seat, peeing, and found evidence during
times that I haven't been home that he must have used the facilities.
 The problem is that he's generalized the idea to understand that
any sort of bowl-like receptacle, especially if it contains water, is
an acceptable substitute.  He pees in the bathroom sinks, in the tub
... (both white porcelain)  ... he was peeing in his water dish for a
while until I replaced it with a tall plastic jug.  I've just moved
into an upscale condo with a lot of beautiful fixtures, including some
very lovely air duct covers and closures for the furnace vents made of,
you guessed it, white porcelain.  I finally figured out why the house
reeked whenever the furnace came on.

I've replaced the more accessible vents with the cheap metal variety.
He still peed in them.  I've put those plastic covers that direct
the air horizontally over the suspect vents, and found that he now pees
AROUND the area, since he can no longer lower his butt into the vent.
Sigh.

All the vets I've talked to say, bring him in for tests to determine
whether or no he has a physiological problem.  I KNOW that this is a
behavioural issue, at least, I'm certain enough that I'd prefer to
work psychology on him rather than pay for several hundred dollars of
tests that will likely offer me nothing.

Does anyone out there have suggestions?