You could title them all "PCE Performance". Or give them each a title ie "PCE Performance" for home page, "News" for news page, "Contact Us" for contact us page, etc. "Untitled" just looks unprofessional
mediocre to me has negative connotations... maybe thats just me. I would suggest "Our customers range from general street car enthusiasts to amateur motor sport competitors". You are right, amateur can also have negative connotations, but in sport it generally means non-professional, ie, not doing it for a living. I'll try and think of some better options but I'm coming up blank atm.
EDIT: yeah entry level could work.
Matter of fact, general English fix up:
It could still be better; it’s been a while since high school . Maybe Shan the English champion can help.