Could be multiple reasons for this. Are you hauling heavy things? Are tires inflated to the correct psi? How’s the maintenance schedule on it? If all these are fine and it’s running rich might want to check the O2 sensors and make sure there are no vacuum leaks

I’d use a screw or a hot soldering iron to melt a hole so that the tip of a screw can catch into it without going too far in if the flat heads don’t work

Find yourself a star station. Lots of non star don’t do them or don’t want to do it because it takes a lot of time. It doesn’t btw. We take the same amount of time 10-15 min if everything is there that we need. Bring it in nice and hot. Driving it on the freeway is best. Especially if it’s been sitting for a while drive it a few days before bringing it in. You might need a carb number for your intake unless it’s a direct replacement for factory original or has all the necessary “connections” for original emission components. Anything after the cats is fine to change and modify. If cats have been replaced make sure you have the emission label or at least you know the engine family so we can look up the eo# on them to make sure they’re California legal.