[Vwdiesel] Intake build up on 98 tdi

[The Lecrones]

I have a 98 tdi and before I installed it I pulled the intake off and cleaned it out,also the intake ports in the head were cleaned .What have you guys been doing to fix this mess from happening again? This engine only had 71k on it and it was really built up on the inside.
What chip do you guys like for these engines? What else for performance.I tried propane on a 1.6td.This really ads a lot of power!
                                                  Jim