ok so when i bought my car the guy had one box installed which still is but i am having issues with the car bugging at about 6 or 7 thousand rpms. yes i checked all my grounds it got 50% better but still not good enough. when you step on it and get to about 6 thousand rmps the temp gauge drops and starts hesitating. also back fire a lot. any thoughts?

 

Sounds like a msd cdi 6al with the rev limiter set at the rpms you stated. Check out (via search of the Google) "msd 6al" find out which one you have (digital or analog). You'll find what you want/need to know about it and what it does. As far as your temp gauge dropping there is prolly a short between your temp sensor wires and the msd box, so the rev limiter cuts the circuit to your temp gauge.

I is just a interwebz mechanic n00b tho so don't hate if I am wrong just stating the more likely cause.

 

Is an old msd 6a. This one doesnt come with any limiter