You killed your cylinder heads and performance. Who told you to do that?
The D-shaped port is there for a reason. It blocks the acoustic pulses that travel back up your exhaust from forcing exhaust gasses back into the cylinder on the next cycle. By removing the flats, you are causing reversion.
You should have only increased the WIDTH of the ports, while leaving most or all of the flats.
D-shaped exhaust ports are used for a reason, and generally kept intact even in performance porting of cylinder heads.
I chose the method I used to port my heads based on several conversations with some really good people at some very respected businesses. Edelbrock in particular, was a great help to me. It might be best if you do some internet searching on Reversion and D-shaped ports.
A search on reversion on this Forum might prove to be rather fulfilling, too.
This topic is about Exhaust Manifold Porting, not Head Porting. We need to get back on topic.