Our 87 760 turbo with 205K miles caughed, and sputtered and blew out sooty exhaust after an engine cleaning at the car wash. We were preparing to replace the wireing harness anyway due to the crumbling sheilding. SO, now, I have Finished installing new wire harness, timing belt,water pump, cleaned intake manifold,sent turbo out for rebuild and balancing, cleaned flame trap. Installed new "iradium" plugs, Verified timing mark is spot on. Put it all together, and it started right up. Idles beautifully and smooth at 900ish RPM in park. 750 in gear. Drives fine at granny speed of 30, 35 mph. Step on it and turbo ramps up to 12O'clock ( only). It SOUNDS like it should be flying like a bat outta hell, but your going, like, 40. On the hwy, it'll cruiz at 60 and if you step on it, it might gradually make it up to 68.

The coil wire on the old wireing harness had no sheilding left at all and I believe were the source of the caughing and sooty stuff spitting out the tail pipe. With that thought, we disconnected the exhaust pipe at the catylitic converter and the turbo reved right up to 2 o'clock. We removed the catyletic converter. and It drove home like a rocket for about 35 miles. Now we can no longer get it to excellerate much after about 35,40 mph. It cruizes fine at granny speed. Could it be the coil? the muffler? computer? Were outta ideas