Every B2B advertiser who has run Performance Max for leads has had the same complaint: the CRM fills with junk. The instinct is to call it broken. It is not. PMax runs across everything Google owns at once, Search, Shopping, YouTube, Display, Gmail, Discover, Maps, and it optimizes to whatever conversion you hand it. Give it a raw form submit and it will go and find the cheapest form submits on the internet. That is exactly what you asked for. You gave it the wrong job.
So you do not fix PMax spam. You fence it. Here are the five layers, and for B2B you need all of them.
1. Negative keywords and brand exclusions
Both are available in Performance Max now, at campaign and account level. Negative keywords stop your ads serving on irrelevant search and shopping queries; brand exclusions are the cleaner control for your own brand and competitor-brand terms, so you stop paying to "capture" traffic that was already yours or was never yours to win. This is the first filter and the fastest to apply.
2. Content and placement exclusions
A large share of PMax junk is not bad search intent, it is bad inventory: accidental taps in mobile games and low-quality apps that register as leads. Tighten content suitability and apply placement exclusions to cut those surfaces. This is the same leak we cover in Performance Max is leaking your budget into mobile apps.
3. Optimize to a qualified conversion, not a raw one
This is the single biggest lever. If PMax optimizes to "form submitted," it will chase form submits. Feed it a qualified signal instead: import offline conversions so it learns from sales-accepted leads, not every fill. Once the optimization event is a real qualified lead, delivery moves toward the traffic that produces them. It also fixes the reporting gap where the platform and the CRM disagree, which we unpack in Google, Meta, and your CRM disagree on conversions.
4. Exclude your known-bad list
You already know who the junk is, because your sales team disqualified them. Upload that list as a Customer Match exclusion so PMax stops going back to the same well. The full play, including why exclusions have no spend gate, is in stop paying to re-acquire the leads your sales team already rejected.
5. Tighten the inputs
Small settings, large effect. Set location targeting to presence, not "presence or interest," so you are not paying for people merely searching about your region. Give PMax a clean first-party audience signal to guide it toward your real buyer profile. And put one qualifying question on the lead form so the tourists self-select out before they ever become a "lead."
The takeaways
- PMax spam is structural: it serves everywhere and optimizes to whatever conversion you give it.
- You fence it, you do not fix it, and you need all five layers, not one.
- The biggest lever is optimizing to a qualified conversion (offline import), not a raw form fill.
- With the stack in place, PMax goes from a spam machine to one of the strongest B2B channels Google has.