Passively Blind?

I reread a few reviews of Songbird today and was struck by the confirmation that I write passively. Not all the time, but that I have more than the recommended dose within the confines of a chapter. I went back to spell/grammar check and did a run through of my document and came up with about 1%. What am I missing? This reviewer is amazingly thorough and has given me wonderful feedback. I don't doubt that I have passive voice in my writing and I don't really believe the grammar check with my surprising 1%. I just don't know how to go through on my own work and find the passive statements.  More than that there are some I just can't figure out how to reword into an active voice without entirely changing the meaning I was attempting to convey.

I wonder if part of the problem is the verb "to be". So often it's assumed that any form of this verb means passive voice - not true (yes, I checked)

So, my opening sentence: I was six when Jace died - is not passive. This sentence breaks down as noun verb adjective prepositional phrase. Even though there is a "to be" verb it's not passive, right? I feel like my head is spinning. It's a conversation I've had with myself and others that never seems to lead anywhere but to more confusion and frustration from me. Am I wrong about this sentence? If I am then I'm more screwed then ever!!

So where is it? How do I find it? This is what the grammar check pulled from my first chapter (an overall 2%passive voice)

His blue Chevy was parked crookedly, one of its front tires pushed up onto the grass.

His eyes were closed and his raspy breathing was barely there.

His words were stilted, coming through between his gasps.

I know why these sentences are passive and I know I could take this sentences and rewrite them, make them active, but to what end? So I don't have any passive voice in my chapter? So that the flow of the action and emotion is disrupted? When does passive become a problem? If 6% is the magic number that agents or editors go by how are they coming up with that? Grammar check?

I suppose what is bothering me the most is that until recently I never thought I wrote passively. I'm truly at a loss. I've taken syntax classing in university and made above average grades in the class. I remember dealing with active vs. passive, but I never had any problems with it. Until now. I would love to have thoughts on this and any pointers would be great!

 On my iPod:

Save this House by Spirit of the West