I just bought an Airfoil for my 1990 Iroc-Z L98 and I am currently bidding on a ported upper TPI plenum.

I am well aware that these are two very small performance upgrades, and I am not concerned with HP increase as much as some choke elimination. So what RPM should the TPI choke at with a foil and a ported upper plenum, otherwise bone stock.

Save up for the SuperRam like me

it will choke at around the same place as stock
an airfoil and ported plenum wont fix what chokes of a tpi intake----the long tube runner design (and small stock runners). you will never get away from that unless you go with a differet design

since you getting a ported plenum you might want to install a fuel pressure regulator and new runners while swapping..

it should up the power band a tad more, closer the redline..

In fact I plan to get the Superram when I have the engine rebuilt
(114,000 miles currently)

But for now, the ported plenum and airfoil were dirt cheap and thought I could squeeze maybe another 300rpm or so but I guess not =(

The reason I'm not getting runners or a base manifold is cause those are the expensive items for the TPI and I'll have those once I buy the Superram in the future. If I ever run into an unpassable deal on some runners like edel, slp, as&m, or tpis for like an unheard price around 150.00 i MIGHT get those.

You could always buy a set of used runners now, and sell them for about the same price once you are ready to get the Superram. If you have about $250 bucks available to buy a set off eBay, you could always get your $$ back on them.
(I know 'cause I haven't been able to pick up a set for less and I've been wanting some runners for awhile now. It's always a $$ thing for some of us. Maybe one day my kids - 6,4, & 1 - will be out of college & I'll have some car funds again!!)

Thats truly an idea.

i got my SLP runners new from sumit for under 200

i got my SLP runners new from sumit for under 200


Some of us missed that deal.

That's what I get for not checking the board for a week or two.

Damn thats a good deal =P
Congrats.

I forgot to ask - even if the foil and ported plenum aren't going to relieve some choke do you think there will any improvement in horsepower? Maybe 5 to the wheels (im dreaming right?)?

You will definately gain some HP. Not sure how much, but I'd guess 5 to 10 HP. Not only at peak, but also in the midranges.

Ok not to shabby for 40 bucks worth of junk =D