I hope you have good solid tooth fillings w/34psig

You might be lucky and have the ratio stamped on the rack, possibly the end caps, but here is a good way to calculate the ratio, but it does require some equipment.

Drive the car on some alignment turntables and set them to zero, both sides. Turn the steering wheel exactly one full turn either way. If the read out is, say 36 degrees (for ease of describing), you then using 360 degrees, then divide with the 36 degrees you then come up with 10:1 (yeah, I know!!). 18 degrees divided into 360 would then be 20:1.

A note though, alignment specs will show different for each side, but you can average (guesstimate) and be close enough.

My guess is that you have the 15:1 making stiff slow speed turning (or maybe it just needs a good grease job