1999 Corolla Ce

Most aftermarket headers don't make any or actually lose power on the 1ZZ-FE - most have gotten much better luck getting the OEM header ported. Some have reported as much as 10-15HP gain on 7th gen Celicas (1ZZ-FED powered) - probably not that much gain for the Corolla, but people swear that porting does make some difference. Some have experimented with cutting the OEM header and adjusting the lengths of the piping to maximize scavenging - but it is a tough, nontrivial process. Most shops just do not have the resources or expertise needed to kick out a decent product.

FOr CAI - not many for the early 8th gen Corollas. EL Prototypes was one of the few that made them specifically for the non-VVTi 1ZZ-FE. But I think the guy sold less then a handful of them (less than 50 total) - he cleared them on eBay some time ago, I don't think he will make them again - just not enough interest with people wanting them. They do have ones by Injen (TRD) for the later 8th gens (2000-2002) - they can be adapted for earlier models, just have to plug off the MAF sensor port and a couple of caps here and there. Might be harder to find - same with brake upgrades and suspension bits from TRD, pretty hard to find.

Honestly, you get pretty decent gains with just a drop in filter upgrade in the OEM airbox. Temperature differential is not that much different between ambient and underhood temps - expecially at speed.