Gs 300 Exhaust Help

[Tony T]

Hi All

I am new to the forum & require your expert assistance.

Three months ago I had a new fabricated stainless steel exhaust fitted to my 1999 GS300 sport, this included a new cat & full system with twin exit pipes per side.

After the fitting of the exhaust I noticed a drop in power through the rev range, at the time I thought that the car may need to adjust itself to the new exhaust, but it hasnt & the power is still down in comparison to the old exhaust.

I have done some investigation & found that the tubing on the new exhaust is only 50mm diameter compared to the 60mm standard exhaust pipe diameter.

Will this have a negative effect upon the car as it breaths???? & should the company have used this diameter pipe or used a 60mm pipe bore.

All help would be much appreciated, I would like some expert advice so that I can then contact the company that did the fabrication.

Kind regards

Tony