turbo upgrade for DD?

Honestly, you can probably just change your current setup around and help out with the lag a decent amount without losing too much power. Two things stand out to me:

3"exhaust ... 2.5" lower intake piping

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That car doesn't need a 3" exhaust - not even close. Drop that to 2.5", maybe even 2.25". This will help a good deal with spool at the cost of a little top end.

The charge pipe is too big, as well, but it's a short enough pipe that it doesn't make a HUGE difference. The turbo's compressor housing outlet is 1.75"; cutting a half inch out of that pipe's diameter will gain you some RPM/responsiveness (you'll have 35% less volume to pressurize). I'm willing to bet that the intercooler is equally too-large, but just changing the piping will help.

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Those are the two biggest things that helped me on my Cobalt. A huge exhaust is great for top-end, but it will severely cut into the turbo's ability to spool up quickly. Huge charge piping is a waste on a turbo that small, as well - it just increases your lag. You're running the same size exhaust and larger charge piping than what I run on a 450 whp car.

You might be right, but I had a Euro PD150 airbox to turbo pipe and a 2.5" exhaust on my setup, which is not much bigger than stock. Turbo performed the same as the OP's. But as Jeff at Rocketchip says, larger orifices and forced induction don't get along.

Im not sure if the 3" is too big. Diesels love large exhausts at least in all the trucks ive built. Now as far as the charge pipe, what size should I change it to and where should I get it?

It's not "too big" in the sense that you're losing / not gaining power from it; it's too big for a DD that desires more low-end.

While the turbine side doesn't necessarily pressurize, it does rely on some amount of back-pressure for a healthy/early spool. I've run an 18" long dump tube straight off of a turbo before - made great power once spooled and was terrific for drag racing, but it was absolutely gutless in the low-end and made for a terrible street car. Power came like a light switch, just like you're describing... and it came late. Swapped to a proper, full-length exhaust system and picked up 500 rpm of spool. You're not going to gain anything that large, but it will definitely help.

I don't know where you'd get a different sized intake pipe. I made my own system. You probably won't gain much from changing a single pipe, but a small detail like that makes me want to inspect the entire system. How large is the intercooler? The rest of the charge piping?

This is all generalized turbo knowledge. If IndigoBlueWagon says that's just how that particular turbo behaves, I'm very inclined to believe him.

So instead of changing both pipe and exhaust I change to one of these turbos mentioned would it behave like I want or will it still lag? Ive had diesel trucks for a long time but I havent messed with these tdis much.

The effects of turbo lag are much more exaggerated on a smaller engine, so the car will still lag. Even my tune-only 2014 TDI didn't really come alive until 1600-1700 RPM or so, iirc.

You're not going to eliminate lag. The best you can do is cut it down to a lower RPM and maybe make it a less violent/sudden event.

makes sense, thanx for your help

A cheaper first thing to try is to replace the cam with a stock one.
Then get Jeff to tweak the tune.

USMCFieldMP said:

That car doesn't need a 3" exhaust - not even close. Drop that to 2.5", maybe even 2.25". This will help a good deal with spool at the cost of a little top end.

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That statement about the size of the pipes affecting spool is true if referring to the primaries upstream of the turbo, ie. in the exhaust manifold. Downstream there is little downside to large pipes; you are not exploiting gas pulse dynamics and while overkilling it with 3" pipes for, say, a 200 HP power target won't add much benefit, it will not affect it negatively, either (except for boost creep in cases of an undersized turbine).

In short, yes it's true, you don't need a 3" exhaust, but if you're going to do the job and expense of replacing the exhaust system anyway, it won't hurt. Just make sure you can properly clear the rear axle without an unpleasant thump whenever you hit it a big bump.

Thats been my exact experience working on powerstrokes