So less boost to make the same power or slightly more. Because the system is more efficient.
Since I live in a desert. But want to keep my warranty. I’m debating about upgrading my factory intercooler.
Here’s a dumb question for anyone that knows. You know how the factory clutch is almost maxed out on stock power. And it’s recommended to upgrade the clutch when getting the stage 1 tune. So would running a bigger intercooler. (And having full torque or slightly more.) Would that make it to start slipping faster?
When upgrading your components to more efficient components, that in itself DOES NOT void the entire warranty. It obviously voids that specific component, but NOT the entire drivetrain.
Things to avoid (if you're concerned about warranty) are fueling components, turbos and connections directly to them, BOVs, or reprogramming the ECU - just to name a few.
Although, these changes don't "always" apply to warranty, they generally do - and the only recourse is to get fully engaged letigiously.
Onto your clutch question:
I have seen and read of many MT GTIs that are on Stage 1 tunes w/o upgrading the stock clutch - this all depends on WHICH tune you opt for and from WHICH tuner you get it from (if they are OTS). There are Low torque and High torque variations and often users will opt for the Low torque for that specific purpose.
The increase of power is what is applying more contact friction to your transmission. However, on the stock tune you are using the same ECU diagram and adding an IC is simply keeping it from retarding the timing - so you remain optimum.
Conversely, I have seen and read of MT GTIs that burn out their stock clutches w/o any modifications.
If you drive more spiritedly more often and live in a dry/arid region that has extreme high/low temps - ensure you increase your lubrication fluid intervals and that will assist greatly preventing premature wear.
Now, the actual "shifting" part is directly related to the driver.