92 Accord Wagon (auto), Dallas Tx.

Failed inspection 1st time so I poured in a bottle of fuel cleaner (premium gas) and run off 3/4 tank of gas.

It failed again (NOX) by a small margin. I was advised to use up at least 2 cycles of of my gas tank before bringing it in again. Did that but it failed the 3rd time. The margin was worst than the 1st.

A mechanic performed a vacumn test on the line going into the EGR valve. Since engine did not studder he concluded that the EGR ducts in the manifold was clogged.

I took out the intake manifold. The 4 ducts leading into the cylinders coated with gunk but that was easily cleaned up.

The duct leading from the EGR port and branches to a small hole at the top of each manifold cylinder was harder. Due to lack of access i can only pour in carb cleaner. How do i verify that its already unblocked?

I read something somewhere about the ports need to be drilled and pulled out with a slide hammer.

Anybody have any idea?