misfiring?

[88 5.0 hi perf]

hey guys, after i put on the gt40, it ran really good until about 3 days when it started feeling like the car either wasent getting enough fuel or not enough spark. around 1500 rpms to 2000, in any gear the car jerks and makes loud popping sounds from the motor. what could this be? also when i swapped the pcv valve to the gt40, it was a little short from the lower so i have it kind of resting at the top of the hole pointing towards it. could this be the problem mabye because of vaccum? please help thanks in advance.

 

[nito88stang]

sound like a vacuum leak or intake leak, make sure you torque everything down to spec and nothing is unplugged. Get real close to the intake and listen for any leaks.