I can crawl up steep hilly trails (not the rockies..) here in Ontario with our vast Canadian shield exposure with ease.
I also now with the addition of my trailer hitch, routinely pull about 16-1700lbs behind me. I have no issue hauling it and can still nearly idle it around, up grades even.. All thanks to the k03 boosting so low.
yes, the k03/gt-15 sized turbo's are great for daily-ing.
The main problem I have with 1.9TD's with these turbo's is clutch slip due to huge low rpm torque :-(
I think something is wrong. Mine had turbo lag after the I/C but I had 5-7lbs by 2,200 rpm with the k24. I never had to ride the clutch to get up a hill. It was sluggish to get going compared to my TDI which has a vnt and stage 2 tune now, but it still had power. I guess what I am saying it was not quick off the line, but it still had power. If I put it in first and went up a hill it pulled just fine, but especially with the 3.67 ring and pinion I couldn't peel the tires off unless it was wet. I could start even on most grades by just letting the clutch out, so it had torque. Is this what you experience or is it worse? If it is worse I would say something is off. If it is like this I would say it is normal.
Just read the other guys posts and if you are talking about going up hills at speeds not starting off, shift. Match the torque of what you need to the speed you are going. Mine would lug up a hill at 40mph in 5th, but I wouldn't gain speed/wouldn't lose speed. If I wanted to gain faster I would shift to 4th, if I wanted faster yet then 3rd, and if I wanted stupidness I would get 2nd until the pump quit at 53mph or so and go through them all.
I agree something doesn't sound right maybe do compression test and double check can to flywheel timing
Make sure you aren't experiencing major boost leaks, the "blow-off" overpressure valve is a big source of them.