I have double wishbone front suspension, rack and pinion steering, KPI is 11 degrees and caster is 5 degrees, tires are 315/30-18 and toe is 1/8 total toe in. The steering is way too light and I have tried an adjustable flow control valve on the power steering and it worked great on the road but made parallel parking impossible. Should I just increase caster to get some steering feel back?

I have double wishbone front suspension, rack and pinion steering, KPI is 11 degrees and caster is 5 degrees, tires are 315/30-18 and toe is 1/8 total toe in. The steering is way too light and I have tried an adjustable flow control valve on the power steering and it worked great on the road but made parallel parking impossible. Should I just increase caster to get some steering feel back?

Apologies the site was down.  Got hacked.  All good now.

You are absolutely correct in that caster will increase steering feel.  Plus with 11° of KPI angle, I suspect you're seeing the inside front tire camber inward alot, reducing your inside tire's contact patch. I believe if you bump the caster up to 10-12°, you'll see the inside front tire keeping a better, more full contact patch when turning.  Especially on tight corners.

Assuming you have the outside front tire working optimally right now, you'll need to reduce your static camber with the additional caster, to keep the outside front tire contact pact happy.

On a different note, if we reduce the scrub radius on race cars with low caster, the "feel" in the steering reduces.  When we increase the caster, the feel comes back, AND we now have the absolute best tire contact patch & overall front grip. In my experience, low scrub radius & high caster go hand-in-hand to creates the best overall front grip.