Burning oil? M103

[John5788]

ive noticed that my 1993 2.6 M103 motor has been consuming a lot more oil since I've installed the 3.27 differential from a 16v (stock in my car is 2.85) and I do alot of highway driving.

I used to only lose 1 quart of oil every 6000 or so miles with the stock differential 3000rpm @ 70mph. but now with the higher gear ratio, the motor is at 3500rpm @ 70mph for highway drives and I lose about a quart of oil every 1500 miles or so.

i have also noticed that when I do let the motor rev higher and higher, my oil consumption goes up more. i believe this might also be the cause of a broken catalytic converter that now have.

the motor has about 144k miles on it, does this sound like a valve stem seal job or should I be looking at something else? i am considering to replace the valve cover gasket, timing cover gasket, and camshaft oil seal if this is the case.