How to Diagnose Memory Issues

my site has been struggling with memory issues for some time now. At first I thought it was the 300k spam comments in the db, but those got nuked and are gone now. Then I thought it could be a plugin but I’ve disabled almost every plugin and that doesn’t seem to change anything. I’ve run the P3 plugin and it doesn’t identify any plugin causing issues other than JetPack, and the memory issues predate JetPack.

I’ve tried all caching and performance enhancing tricks and plugins.

My host says the issue comes with wp-load.php so I’m thinking the issue may be in my theme somewhere, but I don’t know how to diagnose the theme and find where this error might be. For the record, the host says

> You will notice from the above results that the wp-load.pnp is generating
> a lot of hits 31,711 compared to the next highest at 740. The reason for
> this sort of thing is that there’s some option or code or something that
> the javascript needs from the database or from WordPress or whatever.
> This PHP file is, basically, generating the javascript on the fly.
> Usually, the case for this turns out to be something minor. The code
> needs the value from an option, or some flag to turn it on or off. Or
> whatever.

The or whatever is especially helpful.

Can someone here help me diagnose the issue or point me towards a tool that can help? Thanks in advance!