This has all the sounds of a dirty throttle body. I'm going to assume you have tuned this car with OEM parts recently -right? And your battery has clean terminals and reads something more than 12 Volts? Next put your meter on the + side of the coil with the key on but the motor not running, this will tell you if you have a voltage drop somewhere between the battery, the fuse block and the coil. If all looks good in the electrical department. take the "snout" off of the intake and look down the "throat" of the beast. Is it dirty? The best way to clean it is to take the throttle body right off and clean it with a rag and carb cleaner. Buy a gasket for it first. Don't use a tooth brush and carb cleaner, or you get bristles in your engine when the carb cleaner eats the plastic of the tooth brush. Another more complete intake cleaning system is a service called "moto-vac" I know, it sounds like a scam, but it really works. They take off your fuel line and connect up their machine to your intake. They feed your car a detergent rich mixture that cleans the intake and injectors. The valves and upper combustion chamber is decarbonized at the same time. I was skeptical until I drove it away and noticed it started easier, idled smoother was more responsive. I have them do it every two years, or about 30,000 miles.