TR HP, What changed over the years

US TR's never even made 380.

The US car had different cam timing, lower compression and slightly different ignition timing curve. The non cat cars for whatever market obviously had no cats or precats but they also had longer primary tubes on their exhaust manifolds. There were a few other differences but did not effect HP.

TR512's have more cam (CIS injection not only is a big impediment all by itself due to its interference with air induction, it also will not tolerate anything but a very mild cam), more compression and a vastly improved electronic engine management system that provided far better ignition and injection. The result was far superior throttle response, HP and torque at every RPM.

Sadly on a CIS car not a great deal can be done short of nitrous or turbocharging. Retiming the cams nets little and makes the car intolerent of cats. The ignition advance curve can be reprogrammed in a few minutes but nets very little. The expense of changing the pistons is hard to justify cost wise for the gain to be had.

For the cost of getting any real gain you could probably sell your TR and upgrade to a TR512 and get far better handling and brakes in the bargin.

 

Makes your wallet lighter.

If you get straight pipes to replace those rather badly designed precats and leave the main cats it will still pass smog and run a little better. That and the muffler itself are probably the 2 things that are the most cost effective, produce the best gains (meager as they may be) and still allow you to pass smog. Fooling with cam timing can do some good but it is expensive and is a smog/cat issue.