Ok, ona 12a there are 4 ports for fuel, 2 primary, 2 secondary, two little holes for coolant, and 2 little indentations between the secondarys and the coolant, and the bottom hole. What is the bottom hole for? And the 2 little indentations?

 

The square hole in the middle channels air from the smog pump/ACV,down to the exhaust ports.Its the air injection system that cleans up the exhaust.The Air Control Valve sends the pumped air to the exhaust ports via that hole,to the aircleaner or to the catylitic convertor,depending on throttle,rpms,temp,ect.....

 

so if I were to remove all emissions and replace my cats with a RB cat replacement pipe, could I just weld this shut or would I creat problems?

 

No need,just install a block off plate where the ACV goes.