I just got my gsr swap done and it seems to be slow until 6grand i need help bad i dont know what else to do i had a skunk 2 manifold but replaced with factory and i have a megan racing 4-1 header and msd whats my prblem?

 

i dunno if this could be it...but i lost power due to a new small cat converter...but i dunno if thats ur case..what exhust u running?

 

are you throwing any codes? could be your ecu, which one are you running? might be a problem there or timing