I have an '07 mustang gt and I purchased a digital tachometer for it with a shift light. The install instructions say to find the tach signal from the computer and attach the green wire to it. Here's where I need the help. I've removed the dash cluster and can't find any wire to the tach. I've tried the coil packs, I get a signal, but it is not right. Someone told me to try the two red wires attached together in the fuse box in the lime green cluster, no signal at all. Any ideas where I can get a reliable tach signal for this car? According to the instructions, I do not need a tach adapter, already installed in the digital tach. Help, Help, Help!

 

Suggest you do a search on the various Mustang Forums.
There had been a few topics on adding a shift light to the newer Mustangs.
I don't remember details, but I think you'll have to tap off either the computer,or a somewhere in the engine bay.

 

search function is your friend.