I have talked to mechanic of doing a custome 2.5" inch pipe without the catback, he said it will cause back pressure amd i will loose torque...Anybody know about this?

 

accually you would loose backpressure, which does mean a loss of torque. 2.5 is what most people, and aftermarket companies, use. It seems the best comprimise between loss of torque down low to gain of hp higher in the rev range.

 

So what do you suggest? Pipe or no?

 

I would get one, If you go custom make sure it is mandral bent, if it is bent using compression you will end up with corners that are only 75% of the straight diameter. If you can't find a shop to make one you can ge one through http://www.warpspeedperformance.com If you are looking for power gains I would suggest getting a Y-Pipe, the stock design sucks, I have heard that a new one will give you the most hp gain than any other bolt on.