Have you found that the first shot your take using your Impulse seems to exit the barrel only to travel 10 feet in front of you? If so then your Impulse has what we call first shot drop off, or simply FSDO for short. This is a problem that has long-since plagued Impulses far and wide.
Although there are differing opinions as to exactly what causes FSDO, it can be any combination of the following factors with Impulses, each will be explained.
Dry or over-greased ram:
If you have over or undergreased your Impusle's ram, it may lead to slight FSDO. Unfortunately the only way to remedy this would be to spend a good day exparimenting with varying levels of grease, inbetween removing the firing assembly to apply the new coat...needless to say this is way too much work for somebody to do. The other problem is it would require periodic cleaning and re-greasing of the ram, perhaps even between games. Bottomline, just know that this may be the cause of your FSDO, so you may desire to purchase a new ram such as the NEW DeSIGNZ Slickshot. It is not a guarenteed fix, though.
Over or under-greased soleniod spool:
Similary, if you have applied too much grease to the o-rings on your solenoid's spool, it may be causing FSDO. The solution to this is to clean it apply only a thin coat, or you may try cleaning the grease off and not applying a new coat at all. However remember that not greasing your solenoid spool may cause inconsistencies in velocity due to leaking of air through the spool.
Solenoid voltage drop:
My experimentation has shown that many cases of FSDO are caused by a voltage drop leading to the solenoid for the first shot. This can be caused by any number of problems, however can only be fixed by the purchase of a new board for the marker. Specifically, any board that includes ABS (anti-bolt stick) software will have the unique ability to not only guard against FSDO, but directly combat it as well. ABS will increase the dwell of the first shot to compensate for any o-ring stiction. An example of a board which offers ABS is the KM2 Predator2 board.
Temporary Expansion of the Valve Retension Spring:
Several users have done expariments with their valve springs. They contest that by clipping off a small amount of the coil, FSDO will be removed after they re-dwell the marker. The only problem is this also tends to cause inconsistencies due to the awkward shape of the spring. This is not a guarenteed fix, however, and if you menage to clip too much from the spring you will need to puchase a new one.
Temporary Expansion of the Soleniod Core Retension Spring:
The same symptom may be occuring to the spring around the end of the solenoid core, however this is only my theory. If it proves true, there would be no way of fixing the problem.
Under-regulated Solenoid Pressure / Improper Soleniod Core Retention Spring:
The addition of an LPR to your soleniod may reduce FSDO. This has to do with the recharge of the LPR and other boring statistics. However let it be said that Impulses with LPR's installed should also install a low-pressure soleniod core spring as well. This is the small spreing that goes around the exposed end of the iron core of the solenoid when you disassemble it. Impulse solenoids ship from the factory with the high-pressure core spring installed, which is designed to operate the solenoid at pressures above 100-psi (however they often leak after 200-psi). However, Impulses with LPR's often operate the solenoid at sub-100 psi levels, so the addition of the low-pressure spring is highly recommended. Some players have completely dissolved any traces of FSDO after installing the low pressure spring. LP core springs costs $7 from myself and airsoldier.com.