has anyone did a 3400 swap  turbo. if so did you still us the stock harness.?

yea, You have to lengthen the throttle body wires.

Jud has, and  lots of guys over on v6z24.com

Talk with GPSE3400 over on 60degreev6.com.  He had done two cars with a 3400, 89 gpse and a 92 DOHC SE  both were refit if 3400s.  He can also tell you how to build the engine with crazy 12:1 compression if you want ;)  One of the most knowledgeable guys I know on this subject.

BTW see sig....he also helped me put the 3400 on my girlfriends 97 skylark GS.

Ken