I installed Kumho Ecsta LE Sport tires & new coilovers with an alignment few months ago.

Car handles great (compared to 100k-mile oem shocks) but tires recently started to make screeching noise in tight turns.
I liked when tires gave me a sign of letting-go near the limit, however now this happens too early.

As left side makes more noise, is it alignment problem?

 

It's usually an alignment issue... Probably toe out issue. Don't quote me on it, but if they're sport tires, they usually don't screech that easily. Has this been an issue ever since the alignment? I've seen the OE specs of the alignment and the fronts could be into specs with toe out too which I found weird. So alignment shops usually get lazy unless you stare at them and tell them what you want.
Sometimes smooth pavements cause that too, but that's obvious.

 

Its your tires, Every tire acts differently when pushed. Typically UHP and max performance tires make a bunch of noise when close to the limit and while breaking the limit of adhesion. This varies brand to brand and compound to compound so every tire is different.

 

Tires. Every tire is different. Lower performance tiires will scream more.

Having said that, the RE-11 I just mounted are by far noiser that the StarSpecs, RS-3, AD-08 and P-Zeros I've used.