How much hp can a tpi box handle?

Not sure of a hp number here, but Id just like to mention this: on a stock/ mild build the stock box is probably OK if its "persuaded" into doing so. If you look at your entire air intake setup, you'll see it is incredibly restrictive, and the fact that a 350 was supposed to run efficiently with that setup is beyond me.

Ive already described this before, and i suppose I should make this into a FAQ!

Heres what to do:

If you take the "Y" housing off, you'll see the plastic part the air filters sit in. If you take the filters out, you'll see more plastic lol, there should be "fins" that say something like "replace with ac (or maybe ac delco) filters". What you want to do is take this entire plastic part off and take the "fins" off (two small screws), then with a dremel or similar cutting device, cut the bottoms out of the plastic part. I left about an inch, so when i put the filters back in they sit flush with the part you just cut (the side of the filter doesnt suck air in anyways!).

After thats done, you have just helped increase your air flow BIG TIME, but its still not over.

NEXT, you want to grab your "Y" housing. What you do here is cut rectangular "windows" into both sides (facing engine). This makes it much easier to breath! I put mesh over the holes so its not wide open, but still helps big time! (I did this first actually, and when i test drove it i was giddy with the amount of power gained, especially top end! )

Then, you can mod the MAF. There are screens on either side, an unnecissary restriction. Cut the back (or both) out to free up the air flow. I left the front one, just because my car is my DD and i wanted to air on the safe side Ive read where people cut out the cooling fins, but i dont recommend this for a few reasons.

I ordered a Throttle Body Air Foil, supposed to make better throttle response, better mpgs, ect ect. I put it on, it was horrible!! It bogged my engine down so bad, i could hardly break the tires free to do a burnout! Felt like i went from 8 to 4 cyl. I put an uncut "Y" housing on and it helped a little, but still felt like it was only 4 cyl. If you want to give it a try feel free, but i personally DONT recommend, i couldnt get that thing off fast enough. Others also have said it didnt help any unless heavily moded engine, and even then it was negligable.

Of course, K&N box-stock replacement filters here are a must.

Ill probably make the FAQ tomorrow, pictures included . Keep an eye out for it, ill also post other ways to make more power out of your TPI engine

If you lost power with the airfoil, then you did something wrong. While I agree they don't actually "help" much, they also don't hurt. If you lost power at all, I'd be surprised. To lose so much that you could feel?!?!?!! ....something else is wrong here.

....as for everything else? The entire system from airbox to manifold is pretty restrictive. And like the saying goes, you're only as strong as your weakest link. If you have a stock TPI, then the "Y" airbox is just fine. Lots of guys running mild to moderate engines with the stock airbox and no issues.

Its pretty hard to screw up the install of an airfoil...

When i put the uncut Y intake back on it seemed to help, but still sucked. My intake setup now is great, its more than suffecient. It really roars when it gets to the higher rpms, its audible even over the exhaust! lol

I was considering trying a conical K&N, but to be honest, i dont think its worth it. Im more than happy with my current setup for now, once i start dealing with bigger hp numbers i may need to work on something tho. Like you said tho, mild built engines are still ok with the stock setup so an opened up setup should be enough

I wasn't actually suggesting that you messed up the install of the airfoil, but that maybe something else happened during the install. A harness that you forgot to reconnect, vaccuum line, anything. I know I've done it before LOL! ....my point was simply that an airfoil won't cause you to lose power. ....or gain power. At least not enough that you can feel. The dyno may detect a difference, but you won't see it on the "butt" dyno.

Just get a filter like the new ramjet crate engines have. Stock intake is extremely restrictive, I gain at least 20 hp with no piping whatsoever.

Only the 90-92 cars (speed density) can be run with just a filter. All the others require the MAF sensor. 20hp? On a 305!?!? Wow. Your intake musta been EXTRA restrictive.

Oh sorry, I should've read what was after the pic, I thought he was talking about his 91. And yes, it is extremely restrictive and the gain is that noticeable.

doesnt hawks sell a gutted airbox really cheap for are cars?

Nope, evrything was right. I checked, and double checked lol. The guy i bought it from (ebay) said the computer has to "adjust" to it, but after i read reviews about them I just wanted my $30 back lol

Why buy one from hawks for >$100 im sure when you can cut it out for free and cut all the other stuff within 15-20min?

lol sorry tho, i dont see a 20hp gain from just that filter though, especially with stock engine and exhaust even, even harder to believe on a 305. Even with a built 305, still hard to believe

No filter, just tb. I have a 3 inch exhaust but not headers, as well as a shorter belt...no a/c or smog pump pulley.