91LX - Since nobody else has responded I'll throw my lame 2 cents in. I'm a little confused by your post. Are you comparing your car to your brothers car or comparing the same car? It sounds like the same car. Anyways, if your question boils down to comparing the same car it sounds like the issue is the car ran 97 mph stock and now with all your mods it still runs 97 mph. I could be wrong but most of the stock '99+ GT's I've seen at the track run low to mid 90 mph's. I know folks are going to get on and say they've seen stock '99's run upper 90's and even 100, but everytime I've been to the track that's what I've seen (then again I'm in FL and it has always been in the high 80's temperature wise). So if your car is one of the lucky stock ones which run upper 90's, then your mods (especially the chip upgrade) would be just an even swap possibly. From all I've read the '99+ cars have pretty decent exhaust systems, so unless your blowing or gassing your car the exhaust work won't get you too much (I'm sure it sounds faster though
!) I'm not sure what 22C plugs are, but I've never heard of a plug upgrade doing much for performance (actually measured at the track, not the butt dyno), unless the replaced plugs were shot. I would say if you put a SC or nitro on your car the exhaust and LMAF would help, but doing this just on a stock car might not help as much as you would think. Also was the chip programmed to handle the exhaust and LMAF? I made only three mods to my car and gained .4 seconds and 5 mph (LMAS and Anderson PowerPipe, and Diablo Chip), however the chip was specifically tuned for the other two mods (and my car is SC'ed). If the chips doesn't know about the mods you've done, you won't get as much gain. Well there's my 2 center of rambling and I'm sure it didn't help much. Your idea of running at the track back in stock configuration and then swapping the mods back on sounds like a good idea. I'm curious to here of the results, keep us posted and good luck with this.