Hey all. I have an 89 Skyline GTS-T, I've had it for about 8 months now. I am having a very odd problem. When I first got the car imported, it was completely stock except for an aftermarket exhaust. The car ran PERFECT, about 3 weeks ago, I cleaned the motor and did some dressing up with new hoses, etc. Ever since then, whenever I'm driving, Once I hit 4th gear, the car seems to lose a ton of power for about 5 seconds, then it picks right back up. But for those 5 seconds, it literally feels like the motor has just died. What could I have done? Thanks. I really dont want to take it to an expensive shop if it's something simple I can fix.