If it isn't broke don't fix it.

On a 2014 Tdi a worthwhile thing to do would be to check if your intake air pipe to the manifold & throttle valve are blocked with oil laden soot. If so and after cleaning it out the performance will be noticeably improved.

VW Touareg Tdi - coolant leak test part1 - YouTube from 1.05

(3) Soot inlet manifold. | Volkswagen Touareg Forum (mytreg.com)

 

if the way you propose worked better than the current system, VW would’ve done it that way. I’m sure they spent a lot of money on R&D of the intercooler system.

 

each intercooler is made to take about half the airflow. One won't do it, simple as that.

even if you live in the north pole, one is not designed to take that much airflow. The result will be a greater pressure drop... loss of performance. It might spool a hair faster, but will greatly compromise everywhere else.

 

Dual side mount intercoolers are FAR from rare in German cars.

With that said, what others have said, cutting down to one stock side mount ic will NOT work.

 

I'm not suggesting cutting down to one, my idea was to run the routing through both, but in series rather than parallel.
The air routing would be as such:
Turbo -> RH intercooler -> LH intercooler -> intake manifold

Rather than split the air 50/50 between both coolers, run the air through both sequentially

 

But the intercoolers are only meant to flow a certain amount of air volume efficiently. With your proposal, you’d be running all the air through 1 intercooler.
If you want to run 1 intercooler, convert to a large front mount. Otherwise you’re just wasting time.

 

I agree with that. Or, run some monster dual side mounts in place but there is nothing I've been able to find that fits absolutely perfectly dimensionally that would be an upgrade. The Porsche has ever so slightly larger ones but they never panned out to produce any more power in the Touareg

 

A longer intake tract is also going to introduce more turbo lag, which is not desirable in a street vehicle.

 

I figured there would be less lag since the overall volume in the system would be reduced. Less air to move = less lag