88 Shelby Problems

[BAKES]

i would check the plastic vacuum lines be carefull they are more than likey they have gotten very brittle check end to end i have replace many of them mostly because some one did a head gaskets and tryed to move them

[NAJ]

The baro solenoid is a 3 port universal solenoid,vacuum in, vacuum out and a vent(remains open)The part # for my 1990 is 5234217 and is still available from Mopar,list price is $31.00,call your dealer to see if it fits an 88.
Be sure you have 16-20"hg coming in to the baro(if not repair the vacuum problem),from the baro to the map,if you do the baro solenoid is not faulty and is not the reason for your code 13.
Here are diagnostics for code 13,this is from a 1990 manual so controller pin locations will be different,use the connector pin out for 88.

[1993CobraGT40]

BAKES, thanks for taking the time and looking at the part. NAJ thanks for posting the pictures. I won't be able to get over to the car for another two weeks (at my dads) but will try what you posted. I am anxious to go over the vacuum lines again and see if I missed something. Again, I appreciate the help. Great site!