char request[1];
What advantage does a one element array offer over a scalar variable?
Why are you passing a non-NULL terminated array of chars to a function (atoi()) that expects a NULL terminated array of chars?
Serial.print("\n\r");
You don't like Serial.println()? It prints the carriage return and line feed in the proper order. Is that what you don't like?
If I use 9 sensors/input the output is fine, but when more than 9 say 10 sensors the error is begin.
How are you passing 10 as a single character?
char buf0[1000], buf1[1000], buf2[1000], buf3[1000],buf4[1000], buf5[1000],buf6[1000], buf7[1000], buf8[1000], buf9[1000],buf10[1000], buf11[1000],buf12[1000], buf13[1000],buf14[1000], buf15[1000];
You think that there's a snowball's chance in hell of the Arduino sending 1000 characters to represent the value read from ONE analog pin? Get real.