Vent Fan speeds (help)
 

1988 Corvette, C-4. The vent fan works for both heat and ac, and will sequence thru all 10 fan speeds. However, at max fan speed, 10, it feels like it may be pushing air only at about speed 5. And every speed from 10 to 1 has the same ratio, about 1/2 as much air moving as I feel there should be.
I have taken the car in to Corvettes of Houston. The service manager first agreed with me, he said he felt there should be more air moving thru the vents. He suspected an air duct had come loose somewhere behind the dash, should be an easy fix. But after getting the car in the shop, and his mechanic looked at it, the mechanic said there was no problem, that even with 10 different fan speeds, that is all the air it should be pushing thru the system.
Is there a history or precedence of this? Is that vent fan or air ducting set up in the C-4 just a relatively low volume system? Considering there are 10 speeds, and it is a small cockpit, I would suspect there should be an ample amount of air movement. I owned a C-4 about 9 yrs ago, and did not recall the air flow to be less than adequate. Maybe I dont remember that well. But again, this mechanic says there is nothing to be done to it, the low air flow is normal, and is comparable to like models they had in the shop.
Any thoughts or ideas from the experts here on whether this is true, or if anything else can be done?
Thank you.