A/C front not blowing at highway speeds

[mpicasso]

Have looked but have not seen anyone with same issue:

2006 Yukon XL Denali

When driving on highway for a period of time, front A/C vents stop blowing at the levels they should. Cycle to floor/defrost and nothing changes. Slow down to city driving and in less than 5 minutes, fan blows normal.

Do not recall having an issue with rear fans.

Not sure where/what to check as I cannot reproduce the results when at home.

Thanks in advance!!!

 

[mpicasso]

Took to mechanic for some diagnostics which really did not get me much further.

B0228 recirc door in dash for ac system

C0131 abs/tcs system pressure check fault
- states he is not sure how to fix

Any help on either of these would be appreciated.