Ok, a couple things. I have some experience in this area (
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=50589&hilit=+intercooler).
A small leak will not hurt your power because the MAP sensor will still maintain the needed PSI for the system, however it WILL cause your turbo to work harder. I.E. If the ECU requests 20PSI, and 20 is being read at the MAP sensor, but 5 psi is being lost then the turbo is producing 25psi and working harder than it should. Obviously this is not good. A large leak and this gets worse, etc, etc.
If you leak is fairly small like mine was you will notice that if you use curise control the vehicle will surge becuase air pressure is being lost through the leak in a rythym while pressure is built, with the higher pressure it leaks faster, then pressure is lost, then turbo compensates and adds boost to maintain the ECU's...over and over. This caused a slight surging of rpms/vehicle speed.
Anyway, I ended up getting an intercooler from someone that bought one to build a salvage jeep and then gave up adn sold a brand new one to me. Welding it can be tricky since it has plastic end caps. I had an offer of one guy to build alumimum end caps, build the outlets, etc, fix the leak for me for $500. I got the new intercooler super cheap at $300 so i swayed that way.
If I had to choose the $700 or 500 for repairing mine and getting metal end caps for a perminate solution I'd go with the all metal solution.
These intercoolers arent really known for issues that I know of, but most people don't notice the surging or think its normal so no one knows till they take theirs out and see a black spot on it. So who knows? There may be a bunch of bad ones out there? I pressure tested the new one to 30psi and it held perfectly so i knew it would be good to go.
Drove like a dream after that...for more on that project see the above linked thread.
- Mark