one of my string leeches(sp) blew off last year an im still shootin with jus one on the top...will this cause some kinda of tuning problem only shoot with one leech(sp) at the top of the string?????

No, not that you will notice.

good..wasnt sure if the extra weight on top could throw something outta wack or not

nope youre fine.

I serve inmy leeches because i have lost several from them just coming out of the string during the shot. Does't take much just above and below each with serving thread.

It really depends on how well your bow is tuned/balanced as to whether or not you'll notice any problems. In most cases you won't notice too much of a difference.