Civic Hx Lean Burn Problems
 

Having some problems with my 98 Civic Hx manual. Started with what I thought was a cracked exhaust manifold but I replaced the exhaust and it continued. Lean burn constantly engages and disengages. I replaced the air fuel ratio sensor with a new NTK 24300 LZA-09, I also replaced the rear o2. When lean burn engages the A/F ratio goes to 22:1 and within seconds lean burn disengages and reengages, over and over again. When it does this the engine "surges", naturally this is very annoying. Anyone have any ideas whats going on?

New NGK heat range 4 plugs, new EGR valve within the last year and cleaned out the ports.