Trimming up the one drive goes up alot faster than the other, and the reservoir for that drive look like the fluid has alot of air in it. My question is what causes this ??

Possilble cause:
Could be you have a slow trim pump reservoir leak, and the resultant low oil level allows the pump to suck air. Check for an oil film under the vicinity of that pump. I think the oil reservoir can't breathe properly.

My personal experience:
Imagine the starboard trim pump mounted level, with filler cap at the aft end. Let's say you are moored at a sand bar with your drives fully out. With the bow 'up' attitude, the reservoir oil may be tilted up into the air-vent slots of the reservoir cap, and slowly leak out through the threads. Then when you move your drives inward, the net oil flow into the reservoir pushes more oil out the cap vent because the air is locked in the forward end of the reservoir.

My actual fix:
For $0.65 I bought 1/16" x 2" rubber washer and 1/8" x 12" clear tubing. Drill a hole through center of plastic cap and mount tubing throught the hole. Apply washer to underside of cap. Fill reservoir and screw on the cap. Vertically secure the remaining 11 1/2" tubing. Now the cap will seal the reservoir and the tubing will allow the reservoir to breathe.

So far, no leaks for 2 years.

Good luck.

Thanks, I will give that a try