Okay guys,

I've been experiencing this for almost 2 year now.
And still been asking here and there with no exact answer.
I used to have INPA but last year it went kaput along with the laptop.
So no possible diagnostic during this time.
Recently I've installed Ista+ on laptop for diagnostic. Still new to this software.

Issue:
After a long drive in highway, AC would blow slower and cabin feels warmer.

So today I did a test with ISTA+ hooked up to read some of the parameter.

Testing was done on the following static parameter:
1. Highway speed maintained around 100kmh on cruise control
2. IHKA was set to auto - intensive
3. Both left and right temperature knobs were set to 22C
4. Rear AC not activated
5. Ambient outside temperature of around 26-29C
6. Duration of test approximately 20 minutes

The following info were obtained at the Start of test:
1. Evaporator Temp: around 3-5C
2. Both Heater Temp: around 40-45C
3. Outlet of vent temp: around 5-7C
4. Interior temp: around 20C
5. Refrigerant pressure: around 12 psi
6. Blower bar on the car: 3 bar
7. All flaps reading was 100% except for defrosting around 20 and footwell around 50%.

During the drive, it was observed that the Evaporator Temp was increasing toward 15-16C close to the end of 20 minutes drive.
Consequently Vent Temp also raised to similar value.
Other temp reading was relatively similar.
Cabin remain around 20C
Heater temp around 45C
Blower bar: 4 bar

At the end of the test, below is observed:
1. Evap Temp: up to around 16C
2. Heater Temp: around 45C
3. Vent temp: around 15C
4. Interior temp: around 20C
5. Refrigerant press: down to 8 psi.
6. Blower bar: 4 bar, yet the amount of air blown was significantly lower compared to start of test with 3 bar.
7. All flap reading remain similar to start, except the foot flap now reduced around 30ish

Not long after the test. I used the ISTA+ to trigger blower speed up to 80% as per the available option in the software (only this is available from IHKA ECU. I could not set a custom %).
Then the blower blow harder, I could immediately noticed the difference of air being moved through the vent. Then trigger was cancelled.
Interestingly, after this trigger, Evap temp now down to around 4C and vent temp to around 7-8C. I forget to check the refrigerant pressure though.

Any idea why would the blower go slower? during this highway drive?
And why would the evap temp goes higher? I would assume it's because of the blower was not blowing hard enough even though the bar on the car show 4 bar still.

Could this be an FSR issue?

Funny thing is, after exiting the highway at the end of the test, and going home for the next 10 minutes or so, I did not notice any blower slowdown. My laptop was out of battery during this time so no reading is available.
But when I did city drive, I rarely feel the blower slowdown as well.
Maybe later i'll take another reading to compare.

Other than that, does anybody have a suggestion to do next?
I did change the compressor some times in 2014 though. Could this be a compressor issue? But since evap temp can go as low as 3-4 C during idle, I am waiving compressor issue at the moment.

Car is:
2007 4.8i with IHKA High I believe.
Thanks,