The mechanic that you bought the car from replaced the whole air ride system? What did he replace it with? Used or rebuilt parts? The air ride computer doesn't need any "clearing". He either doesn't know what he's talking about, or he's not being very honest with you.
It sounds like you've got a leaky front airspring/shock assembly or two. I don't think that it's a good idea to drive the car with suspension problems. It's not good for the air ride compressor either.
If you've got a friend that knows Mark VIII's, I think I'd trust him more than that mechanic.