the common question seems to be "do these work?"
the answer is that at the extreme upper end of the TPI rpm range they do make a slight measurable difference in the air flow rates, an improvement that's barely noticeable, except on a dyno, unless you've done some port work, on the intake, plenum, runners and probably only significant if you've swapped to better heads and a more aggressive cam and rear gears so that slight increased air flow provides some true benefits to the combo. added
keep in mind that the stock l98 TPI throttle body flows enough air to easily support 450hp on a properly tuned 350-383, and the slight increase in air flow rates won,t even effect the results until the stock TB starts to become a restriction to making more horse power, and thats not the engines weak link, its the heads, cam and tuned port intake itself that's the major restriction in the engines stock configuration NOT the throttle body
read thru these two threads also
viewtopic.php?f=32&t=546&p=685#p685
viewtopic.php?f=55&t=6893&p=22493&hilit=foils#p22493
http://www.ecklers.com/product.asp?pf_id=26690&dept_id=1770
http://www.gmtips.com/3rd-degree/dox/ti ... screen.htm
like this dyno test
http://www.ws6.com/mod-4.htm
ITS been my experience that their worth maybe 1-2 hp in RARE cases, (certainly Ive never seen the 10-15 hp they advertise) but ONLY at very high engine rpms (5000rpm and up) and only with low restriction air filters and a good tune. if you want to spend $30-$40 get one but don,t expect much results
read thru this, its about an LT1 but much of the info translates too the L98
http://www.ws6.com/mycar.htm
ID suggest doing this mod,
http://www.thirdgen.org/coolantbypass
its worth 5 hp and costs very little to do and you can always reverse it back to stock should you choose too
what most guys mis-understand is that those throttle body air foils potentially do work noticably better ON the stock throttle body with its abrupt entrance angles and on a larger displacement engine configs and when the rpms are higher so the flow rates are effected to a noticably greater degree, but a 350 displacement and having an intake design that basically maxes out on flow at about 4500-5000rpm like a L98, and with its heads that only flow 200 cfm , and a cam thats maxed out at about 5500rpm its basically semi optomistic to think they will provide much improvement.
you might also remember that SAME stock L98 throttle bodies used on the 502 BBC engine with EFI RAM JET INTAKE and it feeds even that engines needs so a 350 has hardly any restriction.
LOOK
http://paceperformance.com/index.asp?PageAction=VIEWPROD&ProdID=65332
