Hmmm.

Reports late last year said the 350 km/hr trains would be re-introduced this year.

http://blog.sina.com.cn/s/blog_88f89f490102w1ox.html

It looks like that hasn't started.

As to why the original slow-up, of course it's possible money was a consideration, but you'll also recall fares were lowered a bit when the speed was reduced.