First of all, nothing's all that wrong with ebay turbo kits. The main problem with them is that the people who buy them usually don't know everything that they need to know in order to properly set up a turbo kit, and in reality would probably ruin a more expensive kit as well. Most ebay kits don't come with any type of oil pressure restrictors, and when they're hooked up see the full oil pressure from the engine...which will cause the seals to blow out. First things first, buy yourself an oil pressure restrictor for $12 off of Ebay, and save your turbo. There's a guy on honda-tech/d-series.org running 10.80's on a turbo'd D16Y8 EG running an Ebay T3/T4. I'm personally going to be running an Ebay bigolfuckin'turbo on my non-vtec SOHC build.
Now, granted, the turbo isn't the only thing included in the Ebay turbo kit. The manifolds tend to be cheaply assembled (however nothing that re-welding and bracing won't fix, which is free if you can weld and cheap if you take it somewhere like a muffler shop), and everyone has horror stories about how their friend's friend read online that someone's SSAC manifold cracked. I've personally seen an Inline Pro manifold crack and a guy's wastegate go bouncing down the track behind him. Again, it's a matter of 'if you set it up RIGHT, you can make it work'.
Ebay BOV's are great, they're cheap and do what they're supposed to. Most of them, however, have 2 springs (a thick one and a thin one). You'll want to remove the thin one; to be 100% honest I'm not quite sure why, but I've learned from MANY hours of research online that they function better with the smaller spring removed.
The only thing I wouldn't use from the ebay turbo kits is the wastegate. Those things just flat out suck.
NOW, on to your original question: how much boost can you run. You can run as much boost as your turbo will make; if it's an Ebay kit then more than likely it's internally wastegated, and if so it'll give you 7-8psi without a boost controller. You can buy a manual boost controller, or make one yourself (look on c-speedracing.com, they have a great writeup on making a DIY boost controller for cheap). With your motor built like you're saying it is, you should be able to push a pretty decent amount of boost IF YOU HAVE IT PROPERLY TUNED. Especially considering that you've got a different compression ratio than stock, and you have different cams than the stock ecu program was designed for, you NEED to have it tuned; otherwise chances are you're going to toast your engine. The easiest /best thing to do would be to find a shop in your area that does dyno tuning and contact them, tell them your setup, and ask their advice. You'll probably spend around $800 or so for the tuning and decent engine management (i.e. Hondata), or the tuner might use a program like eCtune or Crome, which would be a bit cheaper. It all depends on the tuner's preferences.
Whatever you do, with your setup do NOT try to run a stock ECU and a VAFC or an FMU, or any other hack like that; like I said, that's a sure-fire way to destroy your engine.
...and to the guy who said to not go above 15psi without any engine management, if you can get over even 5 psi without any type of modification to your fuel or ignition, I'll buy you a trophy. You can't do it. You just can't.
