I have a Honda CR-V 2000 model, (B20z engine) with standard exhaust header being 2" pipes and then a two into one, at 2.25" through a standard cat and then 2.25" cat back system. I just replaced the exhaust manifold and two into one pipe with a 1.75" high performance exhaust header and 1.75" by two into 2" one pipe with performance extractors. I have noticed that my power, acceloration and response have slightly lagged with the new high flow pipes, could this be due to the slight decrease of pipe size? or is it to do with the standard cat...?

Thanks
Sepetinswenze