OK, I used to have a set of the EQT's, so I'm familiar with them.
On the x-over they say there is a tapped inductor and that the adjustor is labeled by driver size (5.25 and 6.5). I don't know what they mean, maybe a jumper you can set for different mid range sizes?
When looking on the ED site they only showed a LPF on the nine.2 amp. So it's does have a HP as well? What was it set at before and what now? Did that give you some more midbass kick?
There's no need to be in the back when testing the response. It may even be more realistic to sit up front. What audio tracks where you playing to get the sound you measured? Are you using "slow" response and "C" weighting?
So you have the analog signal coming out of the sound card and then to the EQT's? What sound card are you using? What audio player are you using?
I can tell you right off the bat that in these cars the stock tweeter location is not very good. An a-pillar install is the way to go, but this is something to look into later if your serious about sound quality. For right now I would turn off the left speaker and map the right and vice versa. If you want even more accuracy, disconnect one of the tweeter wires and map just one mid, then the other, then map just the tweets. That way you can see what the x-over is doing.
Still, I can't understand why you are getting such big drops in the response. It could be the source material. If you have a CD player laying around you could plug it in as a source and listen to a particular song and then listen to the same song through the PC sound card and see if they sound identical. If so, then you can eliminate the sound card as a problem area.
If after all these checks and the mid/tweets still have these huge swings then I would suggest finding a sound shop that has an RTA and let them take a look. They can play Pink noise which contains all the freqs at the same level and you can see the whole response curve at once. Typically you wouldn't use any of the EQ bands more than absolutely necessary. Most changes should be under 4 or 5 dB with maybe some at 7 or 8 dB, but your curve has huge 20 dB dips which no EQ can cure. This tells me either the measurements are wrong or something else in the equipment is not right. You can try placing the meter on the center console and play back the 800 and 2K notes and see if they still have a 23 dB difference.
Hey, the mids are not hitting the door panel when moving are they? They look prety close in the pics.
If you want to play around with the tweeter location to raise the sounstage and improve the imaging you can try something like I did which is to silicone some flexable metal straps with the tweets on the ends and move them around the a-pillar location.
I found that it sounded so good I flush mounted them in the a-pillar.
It will definetely give you better sound and the money you've spent so far shows you want real good sound. Right now we focus on the mids and then mess with the tweets later.