New to forums, engine won't fire.

[7mslipnslide]

Hello folks! I've got an '89 7M-GTE that won't run. Long story short, I just fixed a code 52, buttoned everything back up, and it won't fire. It's setting a code 12. It has been hesitating randomly under load for a while, getting progressively worse, but it never set a code 12 until now. Only the number 3 coil pack is getting spark, and I switched the igniter and got the same result. I checked the engine ground and it's tight and intact. I checked the wiring to the CPS and it seems fine. I'm thinking the CPS took a crap. I searched the forums, but couldn't find much on code 12 other than TSRM links. What I'm wondering is, has anyone else had this problem or am I barking up the wrong tree? It is quite and expensive tree, after all. Any help would be fantastic. It's been a couple weeks since I've been able to drive it, and I'm getting withdrawals.

Thank you in advance,
---Nick