Insert a simulated Ken Thompson virus into a program
For some other languages, determining If the output of P is valid source code in the language you are using is almost impossible, unless you use/rewrite a compiler. For some other languages you can eval a string and catch for error, if any. However, for Mathematica, it is just check for if the head of the result is a function - Mathematica doesn't allow output invalid function, like 1!-!&amp;.
So,
Mathematica, 209 bytes
(obviously can be golfed more, for example by assign long names to global variables)
With[{p=#,c=With[{p=#,c=6},If[#===&quot;aNouIQ5xKvUfdZVzo0Xs&quot;,&quot;BOOM&quot;,With[{r=p@#},If[Head@r===Head@p,(c/.3!-&gt;c)[r],r]]]&amp;]&amp;},If[#===&quot;aNouIQ5xKvUfdZVzo0Xs&quot;,&quot;BOOM&quot;,With[{r=p@#},If[Head@r===Head@p,(c/.3!-&gt;c)[r],r]]]&amp;]&amp;

The function takes a function as input, and output a function according to the specification.
Note that the input must be a pure function, not something like f[x_] := .... So all Mathematica built-in functions fail the criteria.
Although Mathematica have #0 parameter, I explicitly disallow that in my answer because a quine is not allowed to read the code of itself.
(I thought that question is trivial until I read the third rule)