My fuel injection is the lousy Multi Port upgrade from the spider style. It might be an "upgrade" in GM's eyes but not mine. The long block was installed 3 years back from Jeg's, L31 crate motor. So, it's at least a flat top piston 350, 4 bolt main. The OEM fuel delivery starves the motor from what a 350 is capable of. My 92 GMC 350 had TBI and would run like a scalded dog with nothing but a K&N air filter.
I am curious how I could retro fit a TBI system on my 98 to wake it up?
reloder28...not sure what year you have, but I'm assuming you have the Vortec motor (Tahoe/Yukon years: 96-99, and 2000 Limited) since you mentioned the MPFI spider. It also sounds like you've got some other issues if you're noticing sluggishness comparing pre-/post-MPFI swap performance. The original and upgraded fuel spiders have basically the same flow rates.
That said, unless you're running some type of forced induction, fuel delivery is not your limiting factor, unless you've got a leak or a clogged injector. Perhaps your computer has poor fuel trims, or maybe you need a tune-up (plugs, wires, distributor cap/rotor, ignition module, etc)?
As
zraffz stated, the spider does impede the air flow a little (causes added turbulence) which can be remedied with an intake manifold spacer (see link in my signature). If your budget is quite a bit larger, you can change the intake manifold for a Vortec-compatible version (marine or RAM intake) or change the heads and intake manifold to one that better suits your needs. The latter options would obviously require you ditch the MPFI spider for a "direct" injection setup.
