I do have a cu$tom header on my 85 MR2, and let me tell you about my life. Rap the header. Yes it traps in moisture but how often is it going to get wet, how often do you use the car...we are not talking street cars here. If you want to change the wrapping there is a good winter project The MR2 is very different in the way EVERYTHING is in there. You want to keep the under "hood" temps down as much as possible. The way the pipes have to exit the car leave very little wiggle room, My application ran very close to the oil pan and Norm (MR. MR2 as far as I am conserned) suggested I rap the header as it run right under a main. That is good enough for me. He was on this site quite some time ago as ITAMR2 but I have not talked to him in over a year.