The Subaru SVX World Network - Cutting out at low speed and rumbling/vibration

Ever since I got my SVX, it has had a slight cutting out/hesitation/stumbling upon take off. Runs fine after initial take off. No stumbling or cutting out. Also seems to not have as much power as the other SVX I drove had. Not throwing any codes. Is there a vacuum line/regulator that may be causing this? I've heard of people talking about an IRIS valve. Can someone explain what and where this is? Could this be my problem, the IRIS valve? What about plugs? The previous owner said he never changed them, and he put over 50,000 miles on it. I've only put about 1000 miles on it so far.

Also, under 10mph, when I turn, there is a rumble/vibration in the steering. My power steering is leaking, o-ring. Plan on fixing it this week. Has that happened to anyone else? Is this just my leak causing the vibration?
Hoping it's just the power steering. I did try to check my front differential fluid, and the dipstick is stuck. Any advice on how to get it out? I tried some PB lube, and it didn't work. Could the rumbling/vibration be something to do with my differential? I don't notice anything different when driving under normal speed, just under 10mph I get that wierd vibration. FYI- it's only a small vibration and I can feel it in the steering wheel. It goes away after about 10mph or once there is a load on the motor.