im new here dont know how it all works yet but i have a 95 3500 with 6.5 turbo diesel (http://www.dieselplace.com/forum/showthread.php?t=289906#) its hard to start(cranks for a while) seems to run aright untill hi rpms breaks up. only codes are 18 and 35 but i dont know what they mean and what may be wrong.. the engine lights been on for over a year with this problem and i just drove it as is never got better or worse.. can ANYONE help me??

I had same codes and symptoms. try replacing the optical sensor. Are you mechanically inclined? took me about 45 min to do myself. PM member dieselpro. if you need instructions look here http://www.dieselplace.com/forum/attachment.php?attachmentid=61359&d=1206210902

Code 35 could also be caused by air entry into the fuel.

What kind of fuel are you using?
ULSD cause this issue because of lack of lubricity. Try pouring two cans of STANADYNE fuel enhancer + 12 oz of 2 stroke oil in your tank at next refill and see if it goes better.

i just use regular diesel its been like this for over a year

its in limp mode

Might be your optical sensor as said will92104, but try the lubricity tip first.

will do thanks