Ill rerun the test tomorrow and post the results

You'd record slightly higher compression, on the cylinder with an exhaust valve stuck closed. Compression would appear fine, to the untrained eye.   Look for compression that's a bit TOO good, in comparison to the others.    

Yeah same same - no-fuel/no-spark crank

Just went out and cranked it over. She sounds smooth with no funny spots. It does the same thing with or without the exhaust attached though I can try hollowing out the cat. Ive been driving it daily for about a week and a half like this and ive no change. If it was a cam/lifter/pushrod issue woild it affect compression?

Sparkydave means, use the starter trigger wire with the key in off position. crank it over and hear if the engine goes waaa waaa waaa waaa weeeerrr waaaa  every revolution, a different note on one cylinder.    the fact it has even compression, suggests it should be fine.    if it's been sitting ages (blocked exhaust etc) then it might be a valve sticking or lifter issue here and there. i'd still be inclined to run it more and see if it sorts it self out. 

Can I get the same result by doing a no spark crank?

Valve not opening, due to wiped cam lobe, or collapsed lifter.   Do a no-fuel crank, and listen to the note - is the tone even across 6 cyl's or does it vary in pitch, indicating a problem cylinder?  

Update: I installed the new intake gasket and unsurprisingly no change. Id like to believe that its running better now but it still appears to be down a cylinder. Im gonna pull the rocker cover and see if the valves are doing anything but i doubt that this is the problem. It doesn't make any sense to me with it having good compression and spark. Only thing i can think of would be a wiped or blocked exhaust valve. Any ideas?  

when My cat blocked up in my XF ute, i just unblocked it (unbolted the pipe under the drivers floor) and got a garden hose with a bolt jammed in it and just thrashed it around in there until the pieces were small enough to shoot out when i started the car up.)  my intention was to find another second hand one, but i forgot for 100,000kms then sold the car.  (supposedly they would run better with it in according to the exhaust shop,  and a removed cat is a $10k fine apparently, but a broken one just needs replacement )    if money is tight and you get along with your exhaust shop, he'd probably have an E series muffler laying around he's never going to use (or a second hand one in the bin that some kid has put a noise maker 2000 on in place of) they are slightly bigger pipe size but basically same. 
the mid pipe can be put on apparently from cat back to diff  with slight mods (flange is different due to 2" to 2 and 1/4 possibly?) and tail pipe needs either welding to muffler or bigger section added.    most exhaust shops i've dealt with would have a baffled muffler on the shelf that's a close enough match to the original for probably less than $150 fitted these days. 

Hey fellas I need recommendations on a full stock style exhaust for an xf ute. I was gonna patch up the old one but that plan fell apart when my tailpipe collapsed after reversing through long grass. I only need a cat back exhaust as the rest is still ok. Are there any premade systems i can get on the cheap or is this gonna have to be a custom job. Also in regards to "clearing" the cat are there any downsides to doing it. I live in qld and got a rwc so that's not a problem but will it cause any issues that cant be tuned out or can I hollow it out?