I am working on a friend's 87 and he has installed a racing beat road race header with the s4 pickup tube. it is installed and the ports are actuating but i think they are actuating too early from too much back pressure since he is running it to a y pipe and into a single exhaust cat back.

it won't accelerate in 5th gear at highway speeds 55+mph and is completely gutless. on my fc the ports dont actuate when reving sitting still his will.

has anyone else had a similar issue??

 

what diameter is his exhaust after the header?

 

An NA @55 mph in 5th gear is not going to accelerate, no matter how hard you step on it. The engine just doesn't have torque in that rpm range. Teach him to downshift instead.

 

No.. It will accelerate, maybe not up hill, maybe not fast, but it will..

Doesn't sound like an exhaust or 5th/6th port issue.. Though having them closed at that speed would help it accel.

Can you accel. on the freeway if you disconnect the pickup connection?