Anybody out there running a MSD box on their TBI setup. I am considering doing this as an upgrade for my mild 355 TBI and was wondering if anybody had good results? Or is it just not worth it? And where did you mount it?

Setup below

 

I threw a 6T onto the left inner fender of my '88 K1500 TBI 5.7L.

Had it laying on a shelf in the garage, figured I might as well make it "work for a living".

I have noticed absolutely zero performance gain, but at least the MSD 8876 wire harness makes it a super-easy addition to the TBI vehicles.

If you don't have misfire problems, the MSD is unlikely to make any improvement. If you do have misfire problems, you're typically better-off to FIX THE PROBLEM(s) than to use a spark-box as a crutch while you ignore the root cause of the misfire.

If you don't already own the spark-box, don't go buy one. The only verifiable benefit to a spark-box would be the built-in rev limiter (my 6T needs a separate rev-limiter, do as I say, not as I do.)

 

I put on on my perfectly good running TPI engine in my Van. I noticed a smoother idle, sharper throttle response, and a noticeable amount of low-end torque gain. I was also able to tune lean cruise, well leaner without it misfiring.

 

Smoother idle? The idle of my K1500 couldn't GET any smoother. The TBI cams are so mild. Did you change cams or otherwise modify the engine? (aside from the MSD)