If you look around this website and the internet you'll find MANY issues with TBICHIPS.com, it's hit or miss if he can get it right? I've retuned many of them and people are way happy.
Looking at some of his chips shows why. You'd be pissed if you saw how little is done or how wrong it is!
Your 2500 RPM issue has happened before and linked to worn distributor cap and rotor or faulty EST module, the module issue is even worse if you have one that is not GM! Did you run the new spark plugs wires in factory locations? Or are some taped together, to close to EFI wires or modules?
What I can't explain is why the stock chip runs better? Less power then modified chip is easily explained. If he is getting bad data he tuned bad data and now his chip is worse. If you have the slightest exhaust leak anywhewre before the O2 sensor or a vacuum leak then that is what happened, the reason you don't notice it above 2500 RPM, 30% TPS can be 3 fold. Exhaust pressure is built up and no pulse sucking in air to mess up O2 sensor reading, or your hitting PE (Power Enrichement) which goes Open Loop, so no O2 sensor feedback. Or a faulty TPS reading at that point. Vacuum leak would also not come into play at that point. Why the stock one wants to die coming to a stop is the cam change.
Your nose is a horrible AFR gauge, but if you can smell hydrocarbons then you have no CAT. Without a CAT even a good running motor smells rich because 2 things, your nose sucks as an AFR gauge and no one is used to smelling exhaust without a cat that clears this up.
So check for vacuum leaks.
Verify the EST module is GM, some stores can check these but the test has to be done 3 times and if it fails any it's bad.
Exhaust leak before o2 sensor.
Vacuum gauge can also shed some light, look for steady reading at idle and a smooth transition while accelerating, it will move of course but no shaking... you may have a valve adjusted wrong.
You could post a data log, some guys have datamaster but most around here use TunerPro.
HTH!
Bookmarks