At about 2500 - 3000 rpm the gsl-se i own seems to sputter real bad, if i let off the fuel pedal, it seems to run perfect, or shift into the next gear thereby lowering the rpm same thing, smooth as it is at idle. the cars sat for a number of years and although ive changed the fuel pump and drained the fuel... im guessing the fuel filter? Can someboty validate this sympton as relative to its being blocked or in need of replacement ?

Next issue:

removed the trio of catalictic converters in the stock exhaust setup.. had a 4 foot piece of pipe replacing it installed. In the 6 port rx-7 as in the case with the gsl-se, 2 of the ports are fed by the exhast coming back from that line off of the primary converter.
What to do with the 1 line off of that converter that has the second little one t'ing off of it. And have i affecting the performance base of the car by not choosing to spend 1500 bucks worth of converters from mazda like maybe i should have ?

Thank you for the help guys.

 

Your '6'-ports are inoperative - probably explains why you're seeing some stuttering at higher engine rpm's as well.

The exhaust backpressure tube that comes from the #3 Main Cat is used to provide 2-5psi of pressure to each of 2 '6'-port actuators located on the lower intake manifold. These actuators turn rods that rotate your sleeves in the side housings, and if no pressure is evident, then no rotation is happening - thus, your '6'-ports are not opening at all (default, 0 pressure is closed).

In bypassing your stock cats with a straight pipe, you've shut off your feedback system to open the aux ports for more airflow at higher rpm's. I would also venture to guess that your engine feels anemic above 4000 rpm, also, right? This is due to the inability to pack enough air in there using only 4 ports - the ECU map is off and you're running overly rich.

My suggestion, before you start replacing parts that don't need to be replaced, or following the advice of the locals around here to 'wire' your ports open - check out Mazdatrix for their GSL-SE specific header and presilencer combination. This will net you '6'-ports that still operate as designed along with a nice, smooth transition of power in the top end. You'll also get a nice exhaust note.

For the money, the header/presilencer is a tough combination to beat, and will fix your problem induced though bypassing the factory system. HTH,

 

or use RB's cat replacement pipe for the GSL-SE, which is cheaper and also provides a connection for the actuators.