My wife is from Mantin so I've been going there for more than 10 years since high school.
SF, about the Seremban Siew Pao. I don't eat it much...so no comment.
Another Chinese restaurant got nice food I want to recommend. Zhong Ri restaurant at Kemayan Square near Museum Negeri. There are quite some eatery there. It's just opposite KPJ hospital. The famous curry chicken in bread is also in Kemayan Square. SF it was near the Lotus hotel you stayed last time.
For Breakfast. Got a nice curry chicken Nasi Lemak shop at Oakland also but the tea is so so only.
Another nice Nasi Lemak is in Rembau, my mother hometown. It's only available on Friday morning. I sometimes went all the way to eat there then come back to Seremban to work. The fried chicken is awesome.