Steering Rack And Pinion problems of the 2002 Oldsmobile Aurora

Clunking noise in front end/undercarraige, on turns or bumps, can be felt in steering, since 15000 miles (noticed sometime after imploded gas tank replacement). Four dealers worked on at least 10 times - replaced steering gear, lubed intermediate shaft, replaced strut bearings, replaced intermediate shaft, replaced rear shock - still clunks over bumps and steering grinding noise is back since intermediate shaft replacement. After steering gear replacement at 26750, severe vibration was noticed; took four attemts (3 dealers) to make acceptable finally at 36137. Headlamps flicker intermittently, generator replaced at 30311, 4 dealers say is normal. Fuel filler door still sticks intermittently, at least 3 repair attempts. Car does not feel safe with front end/steering/underbody clunking - feels like some component(s) is defective or prematurely worn out - each dealer made repair attempt, then when unsuccessful said vehicle was normal. One dealer never roadtested vehicle. Last dealer mechanic said needed rack, service manager said vehicle was normal. 43000 miles now - gm area service manager refuses to do any further repairs.