Hello everyone. Have a problem with a 1975 camaro with factory 350. Took motor & trans out to paint engine & compartment. Ran perfect! Did not take distributer out but painted motor on engine stand. New plugs,wires,cap rotor. Fuel pump,water pump.Took original quadrajet 4 barrel off intake. Tilted slightly to clean the outside with carb cleaner. It was never upside down. Put it all together & drove it. Was hesitating & not running good. Did not realize distributer wasent tight & it moved while motor was taken out-in. It's a 4 speed car. Timing supposed to be 6 degrees. I disconnected advance,plugged vac line, motor hot at 900 rpm set timing 6 degrees. In neutral revs normal,sounds good. From a stop driving normal it spits-sputters under a load. it kind of clears up around 2,500 rpm. If I hold it to floor it takes off normal & higher rpms seems fine ? Moved timing to 8,10,12 & same thing ? Has egr valve that tested fine with vac test. Car is original & kept it original. Any suggestions where to start looking ? Is it carb? Had no issues before. Thanks for your time !