1993.5 G20 intake manifold question/problem

[ferrari01]

Have been chasing a rough running condition for ever in this 70 K mile car. All Consult-related items OK. Removed intake manifold (casting number 62J) suspecting carboned EGR ports (behind plugs in manifold) into intake runners. In addition to lots of carbon, I also found that the machined port allowing recycled exhaust gases into the #4 intake runner was approximately twice the size of the same ports for cylinders 1, 2, & 3. I doubt this is normal, but if it is, can someone please explain the reason? If it abnormal, as I suspect, is there a TSB on the subject, or what's the likelihood Infiniti 'good will' an intake manifold since it's an emissions related part?

Thanks for your help and insights!

bw