The great thing about neighbours or anyone who has to regularly put up with our attempts at the language is that they eventually understand what it is we want even if we might be saying anything else.
I believe that the viens t' is not correct.
Je viens (de) t'emprunter un XYZ means I have just borrowed an XYZ from you.
In fact now I am confused as I'm not sure that the tu form goes before or after the verb in this case, maybe je viens d'emprunter un XYZ de toi.
What I say and its probably not correct French, maybe overcomplicated and overpolite (gay) is:
Je viens pour demander si je pourrais emprunter un XYZ.
So what is the correct way of asking "I have come to ask if I could borrow an XYZ from you?"
Or equally "I have come to borrow an XYZ from you?" My apologies if Erics text was correct its only when seeing or hearing things said in a different way that I question my own speech.