Consequences of tuning - emissions

I was wondering what would be the likely emissions consequences of doing some light tuning of the 4.0l HO engine - e.g. K&N, boring the throttle body, changing to a 2000+ air intake?

I remember I had some trouble getting my last car through the emissions test after I'd bored holes in the airbox and added a K&N panel air filter, and would hate to cause more problems if I were to do that (and other things) to this car, especially since my XJ's converted to run on LPG, which would inevitably complicate things.

i wonder how the LPG itself effects emmisions.. have you looked into the regulations in your area? i would almost think they would give it an exemption because LPG is a known "clean fuel".. as far as everything else.. keep the old parts and swap them back on once a year for test day.... how does the engine power compare between the LPG and the gasoline set-up?? its good to see more internation interest here.. welcome..

Why thankyou kind sir...!

I've seen the emissions test done once before over here - what happens is that they test the CO and hydrocarbon content for BOTH the LPG and gas/ petrol. The LPG scores normally come out slightly cleaner, but not as much as you'd imagine. Luckily Jeeps are pretty clean burning engines most of the time. Hmm, that's tempting fate!

Anyway, I'm guessing that the sensors change the fuel mixtures slightly if you tweak things, more so if you uprate the injectors and so forth, which would explain why my old car did what it did when it had more air going in: have you found the HCO/ CO readings differ after mods are done?

One of the things I thought of doing was boring the throttle body, which would be pretty damned hard, and pricey, to change back every year.

Surely somebody's noticed a difference in their emissions since tuning their XJ?!

Re: `nsequences of tpning -`amirsiop

@ actually have not had a test since my tuning. But I'm sure an intake and boring out your TB will not make THAT much of a difference. I'll let you know in a couple of months though....

A lot of us don't have emmisions testing. you could always build an adjustable MAP sensor and lean the engine out for emissions. I don't see a k&N filter and a newe FACTORY intake manifold affecting emmisions all that much.

This is like comparing apples and organges but i have an 88' with 4.0 that has been reabiult bored .030" over and has a "rougher" cam and also had some porting and polishing done. That is just the internal engine mods on the intake and exahust I have a Cone shaped K&N filter where the stock air filter was and i have a high flow muffler called a Raven. I have had these mods for over three years and my xj passes emissions with flying colors it runs at 2% of the limit with nearly no CO and No HCO. I'm have no idea how this may realte to your setup because of the LPG but this is my .02

Jerms