Hello and welcome. I'm sorry you are having these problems....generally the triples are as others say pretty tough engines....the 1200 did have noisy valvegear problems on early versions ...but I havent heard of other folks with intake manifold failure like yours . Currently I run an 06 tiger955i and though long in the tooth it's a good tough motor.....and works out more reliable and much cheaper than the BMW GS series...which have well documented serious problems with clutch wear, rear crank oil seal failures, shaft drive bearing failures, abs failures......the list goes on. Personally I'd persevere with the 1200 triumph but maybe replace the shock.....my tiger runs a wilber rear shock and it really does work well. Best of luck.
I know when I had my Norge (recently written off and replaced with the T120), the rear suspension at 30K was taken apart to be checked and found to be almost dry with no grease. On rebuild a grease nipple was tapped in.... I don't think that Moto Guzzi were/are alone in this practice? Nor Triumph perhaps? And again, the eight valve engines were found to have problems with their valve gear, necessitating, I think, TWO recalls. There were no such issues with the 4 valve engines?
A Tell me about it I ran Guzzis for years till my wife banned them on the grounds that she couldn't bear to see a grown man cry.
Hmmmmm....images. A picture tells a thousand words. Any chance you could post those images? You've got a lot going on here. My valve shims haven't moved in 420000 miles, valve regression is virtually none existant on hardened seats. Also bear in mind that air filters on motorcycles is a fairly new concept in the history of motorcycles. The carbon buildup is a worry, and suggests you have a fueling issue, possibly leading to fuel wash which has a habit of destroying piston rings, as the excess fuel washes the oil out of the rings. Just my thoughts. And welcome, but I'm new myself.