New EGR valve, same problems

I just installed a new EGR valve in my 1996 jimmy 4.3L. I stared to notice the temp gauge acting a little eratic which may or may not be a result of the EGR valve. After A day the car started having the same bogging and hesitation problems. I took the EGR valve off again to check it out. I found no carbon or anything else that was clogging up the valve. I did notice though that there appeared to be part of an old gasket still attached to the motor. I cleaned this off and reinstalled the valve. Since then, everything seems to be ok. I'm wondering if this old gasket could have caused a problem with the seal of the valve which in turn caused all of these other problems?

If the gasket was causing a leak between the 2 ports, it can cause some driveability issues