allright i have putten about prolly 140-150 pounds of dynamat in my car. it has no rattle and is alot louder inside now especially with my 12's. But my question is will that hurt my performance excelleration and make me slower in races?

 

yes, adding weight will slow your car down. dynamat is crazy heavy stuff.

 

subs/dynamat + racing seems like quite a contradiction...

 

how much h.p am i losing from the system and dynamat, hopefully only like 3-4 h.p or less

 

you won't lose horsepower. your power to weight ratio will just be worse. your engine will still make the same power.

think of it as having a 150 pound passenger with you at all times.